1. 25 5月, 2018 21 次提交
    • E
      KVM: arm/arm64: Document KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION · d6c77bd1
      Eric Auger 提交于
      We introduce a new KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attribute in
      KVM_DEV_ARM_VGIC_GRP_ADDR group. It allows userspace to provide the
      base address and size of a redistributor region
      
      Compared to KVM_VGIC_V3_ADDR_TYPE_REDIST, this new attribute allows
      to declare several separate redistributor regions.
      
      So the whole redist space does not need to be contiguous anymore.
      Signed-off-by: NEric Auger <eric.auger@redhat.com>
      Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
      Acked-by: NChristoffer Dall <christoffer.dall@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      d6c77bd1
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      KVM: arm/arm64: Set dist->spis to NULL after kfree · 9153ab72
      Eric Auger 提交于
      in case kvm_vgic_map_resources() fails, typically if the vgic
      distributor is not defined, __kvm_vgic_destroy will be called
      several times. Indeed kvm_vgic_map_resources() is called on
      first vcpu run. As a result dist->spis is freeed more than once
      and on the second time it causes a "kernel BUG at mm/slub.c:3912!"
      
      Set dist->spis to NULL to avoid the crash.
      
      Fixes: ad275b8b ("KVM: arm/arm64: vgic-new: vgic_init: implement
      vgic_init")
      Signed-off-by: NEric Auger <eric.auger@redhat.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NChristoffer Dall <christoffer.dall@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      9153ab72
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      KVM: arm64: Invoke FPSIMD context switch trap from C · cf412b00
      Dave Martin 提交于
      The conversion of the FPSIMD context switch trap code to C has added
      some overhead to calling it, due to the need to save registers that
      the procedure call standard defines as caller-saved.
      
      So, perhaps it is no longer worth invoking this trap handler quite
      so early.
      
      Instead, we can invoke it from fixup_guest_exit(), with little
      likelihood of increasing the overhead much further.
      
      As a convenience, this patch gives __hyp_switch_fpsimd() the same
      return semantics fixup_guest_exit().  For now there is no
      possibility of a spurious FPSIMD trap, so the function always
      returns true, but this allows it to be tail-called with a single
      return statement.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NChristoffer Dall <christoffer.dall@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      cf412b00
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      KVM: arm64: Fold redundant exit code checks out of fixup_guest_exit() · 7846b311
      Dave Martin 提交于
      The entire tail of fixup_guest_exit() is contained in if statements
      of the form if (x && *exit_code == ARM_EXCEPTION_TRAP).  As a result,
      we can check just once and bail out of the function early, allowing
      the remaining if conditions to be simplified.
      
      The only awkward case is where *exit_code is changed to
      ARM_EXCEPTION_EL1_SERROR in the case of an illegal GICv2 CPU
      interface access: in that case, the GICv3 trap handling code is
      skipped using a goto.  This avoids pointlessly evaluating the
      static branch check for the GICv3 case, even though we can't have
      vgic_v2_cpuif_trap and vgic_v3_cpuif_trap true simultaneously
      unless we have a GICv3 and GICv2 on the host: that sounds stupid,
      but I haven't satisfied myself that it can't happen.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NChristoffer Dall <christoffer.dall@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      7846b311
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      KVM: arm64: Remove redundant *exit_code changes in fpsimd_guest_exit() · ba4f4cb0
      Dave Martin 提交于
      In fixup_guest_exit(), there are a couple of cases where after
      checking what the exit code was, we assign it explicitly with the
      value it already had.
      
      Assuming this is not indicative of a bug, these assignments are not
      needed.
      
      This patch removes the redundant assignments, and simplifies some
      if-nesting that becomes trivial as a result.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Acked-by: NChristoffer Dall <christoffer.dall@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      ba4f4cb0
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      KVM: arm64: Remove eager host SVE state saving · 21cdd7fd
      Dave Martin 提交于
      Now that the host SVE context can be saved on demand from Hyp,
      there is no longer any need to save this state in advance before
      entering the guest.
      
      This patch removes the relevant call to
      kvm_fpsimd_flush_cpu_state().
      
      Since the problem that function was intended to solve now no longer
      exists, the function and its dependencies are also deleted.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NChristoffer Dall <christoffer.dall@arm.com>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      21cdd7fd
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      KVM: arm64: Save host SVE context as appropriate · 85acda3b
      Dave Martin 提交于
      This patch adds SVE context saving to the hyp FPSIMD context switch
      path.  This means that it is no longer necessary to save the host
      SVE state in advance of entering the guest, when in use.
      
      In order to avoid adding pointless complexity to the code, VHE is
      assumed if SVE is in use.  VHE is an architectural prerequisite for
      SVE, so there is no good reason to turn CONFIG_ARM64_VHE off in
      kernels that support both SVE and KVM.
      
      Historically, software models exist that can expose the
      architecturally invalid configuration of SVE without VHE, so if
      this situation is detected at kvm_init() time then KVM will be
      disabled.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      85acda3b
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      arm64/sve: Move sve_pffr() to fpsimd.h and make inline · 9a6e5948
      Dave Martin 提交于
      In order to make sve_save_state()/sve_load_state() more easily
      reusable and to get rid of a potential branch on context switch
      critical paths, this patch makes sve_pffr() inline and moves it to
      fpsimd.h.
      
      <asm/processor.h> must be included in fpsimd.h in order to make
      this work, and this creates an #include cycle that is tricky to
      avoid without modifying core code, due to the way the PR_SVE_*()
      prctl helpers are included in the core prctl implementation.
      
      Instead of breaking the cycle, this patch defers inclusion of
      <asm/fpsimd.h> in <asm/processor.h> until the point where it is
      actually needed: i.e., immediately before the prctl definitions.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      9a6e5948
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      arm64/sve: Switch sve_pffr() argument from task to thread · 2cf97d46
      Dave Martin 提交于
      sve_pffr(), which is used to derive the base address used for
      low-level SVE save/restore routines, currently takes the relevant
      task_struct as an argument.
      
      The only accessed fields are actually part of thread_struct, so
      this patch changes the argument type accordingly.  This is done in
      preparation for moving this function to a header, where we do not
      want to have to include <linux/sched.h> due to the consequent
      circular #include problems.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      2cf97d46
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      arm64/sve: Move read_zcr_features() out of cpufeature.h · 31dc52b3
      Dave Martin 提交于
      Having read_zcr_features() inline in cpufeature.h results in that
      header requiring #includes which make it hard to include
      <asm/fpsimd.h> elsewhere without triggering header inclusion
      cycles.
      
      This is not a hot-path function and arguably should not be in
      cpufeature.h in the first place, so this patch moves it to
      fpsimd.c, compiled conditionally if CONFIG_ARM64_SVE=y.
      
      This allows some SVE-related #includes to be dropped from
      cpufeature.h, which will ease future maintenance.
      
      A couple of missing #includes of <asm/fpsimd.h> are exposed by this
      change under arch/arm64/.  This patch adds the missing #includes as
      necessary.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      31dc52b3
    • D
      KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing · e6b673b7
      Dave Martin 提交于
      This patch refactors KVM to align the host and guest FPSIMD
      save/restore logic with each other for arm64.  This reduces the
      number of redundant save/restore operations that must occur, and
      reduces the common-case IRQ blackout time during guest exit storms
      by saving the host state lazily and optimising away the need to
      restore the host state before returning to the run loop.
      
      Four hooks are defined in order to enable this:
      
       * kvm_arch_vcpu_run_map_fp():
         Called on PID change to map necessary bits of current to Hyp.
      
       * kvm_arch_vcpu_load_fp():
         Set up FP/SIMD for entering the KVM run loop (parse as
         "vcpu_load fp").
      
       * kvm_arch_vcpu_ctxsync_fp():
         Get FP/SIMD into a safe state for re-enabling interrupts after a
         guest exit back to the run loop.
      
         For arm64 specifically, this involves updating the host kernel's
         FPSIMD context tracking metadata so that kernel-mode NEON use
         will cause the vcpu's FPSIMD state to be saved back correctly
         into the vcpu struct.  This must be done before re-enabling
         interrupts because kernel-mode NEON may be used by softirqs.
      
       * kvm_arch_vcpu_put_fp():
         Save guest FP/SIMD state back to memory and dissociate from the
         CPU ("vcpu_put fp").
      
      Also, the arm64 FPSIMD context switch code is updated to enable it
      to save back FPSIMD state for a vcpu, not just current.  A few
      helpers drive this:
      
       * fpsimd_bind_state_to_cpu(struct user_fpsimd_state *fp):
         mark this CPU as having context fp (which may belong to a vcpu)
         currently loaded in its registers.  This is the non-task
         equivalent of the static function fpsimd_bind_to_cpu() in
         fpsimd.c.
      
       * task_fpsimd_save():
         exported to allow KVM to save the guest's FPSIMD state back to
         memory on exit from the run loop.
      
       * fpsimd_flush_state():
         invalidate any context's FPSIMD state that is currently loaded.
         Used to disassociate the vcpu from the CPU regs on run loop exit.
      
      These changes allow the run loop to enable interrupts (and thus
      softirqs that may use kernel-mode NEON) without having to save the
      guest's FPSIMD state eagerly.
      
      Some new vcpu_arch fields are added to make all this work.  Because
      host FPSIMD state can now be saved back directly into current's
      thread_struct as appropriate, host_cpu_context is no longer used
      for preserving the FPSIMD state.  However, it is still needed for
      preserving other things such as the host's system registers.  To
      avoid ABI churn, the redundant storage space in host_cpu_context is
      not removed for now.
      
      arch/arm is not addressed by this patch and continues to use its
      current save/restore logic.  It could provide implementations of
      the helpers later if desired.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NChristoffer Dall <christoffer.dall@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      e6b673b7
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      KVM: arm64: Repurpose vcpu_arch.debug_flags for general-purpose flags · fa89d31c
      Dave Martin 提交于
      In struct vcpu_arch, the debug_flags field is used to store
      debug-related flags about the vcpu state.
      
      Since we are about to add some more flags related to FPSIMD and
      SVE, it makes sense to add them to the existing flags field rather
      than adding new fields.  Since there is only one debug_flags flag
      defined so far, there is plenty of free space for expansion.
      
      In preparation for adding more flags, this patch renames the
      debug_flags field to simply "flags", and updates comments
      appropriately.
      
      The flag definitions are also moved to <asm/kvm_host.h>, since
      their presence in <asm/kvm_asm.h> was for purely historical
      reasons:  these definitions are not used from asm any more, and not
      very likely to be as more Hyp asm is migrated to C.
      
      KVM_ARM64_DEBUG_DIRTY_SHIFT has not been used since commit
      1ea66d27 ("arm64: KVM: Move away from the assembly version of
      the world switch"), so this patch gets rid of that too.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NChristoffer Dall <christoffer.dall@arm.com>
      [maz: fixed minor conflict]
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      fa89d31c
    • D
      arm64/sve: Refactor user SVE trap maintenance for external use · 0cff8e77
      Dave Martin 提交于
      In preparation for optimising the way KVM manages switching the
      guest and host FPSIMD state, it is necessary to provide a means for
      code outside arch/arm64/kernel/fpsimd.c to restore the user trap
      configuration for SVE correctly for the current task.
      
      Rather than requiring external code to duplicate the maintenance
      explicitly, this patch moves the trap maintenenace to
      fpsimd_bind_to_cpu(), since it is logically part of the work of
      associating the current task with the cpu.
      
      Because fpsimd_bind_to_cpu() is rather a cryptic name to publish
      alongside fpsimd_bind_state_to_cpu(), the former function is
      renamed to fpsimd_bind_task_to_cpu() to make its purpose more
      explicit.
      
      This patch makes appropriate changes to ensure that
      fpsimd_bind_task_to_cpu() is always called alongside
      task_fpsimd_load(), so that the trap maintenance continues to be
      done in every situation where it was done prior to this patch.
      
      As a side-effect, the metadata updates done by
      fpsimd_bind_task_to_cpu() now change from conditional to
      unconditional in the "already bound" case of sigreturn.  This is
      harmless, and a couple of extra stores on this slow path will not
      impact performance.  I consider this a reasonable price to pay for
      a slightly cleaner interface.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      0cff8e77
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      arm64: fpsimd: Eliminate task->mm checks · df3fb968
      Dave Martin 提交于
      Currently the FPSIMD handling code uses the condition task->mm ==
      NULL as a hint that task has no FPSIMD register context.
      
      The ->mm check is only there to filter out tasks that cannot
      possibly have FPSIMD context loaded, for optimisation purposes.
      Also, TIF_FOREIGN_FPSTATE must always be checked anyway before
      saving FPSIMD context back to memory.  For these reasons, the ->mm
      checks are not useful, providing that TIF_FOREIGN_FPSTATE is
      maintained in a consistent way for all threads.
      
      The context switch logic is already deliberately optimised to defer
      reloads of the regs until ret_to_user (or sigreturn as a special
      case), and save them only if they have been previously loaded.
      These paths are the only places where the wrong_task and wrong_cpu
      conditions can be made false, by calling fpsimd_bind_task_to_cpu().
      Kernel threads by definition never reach these paths.  As a result,
      the wrong_task and wrong_cpu tests in fpsimd_thread_switch() will
      always yield true for kernel threads.
      
      This patch removes the redundant checks and special-case code,
      ensuring that TIF_FOREIGN_FPSTATE is set whenever a kernel thread
      is scheduled in, and ensures that this flag is set for the init
      task.  The fpsimd_flush_task_state() call already present in
      copy_thread() ensures the same for any new task.
      
      With TIF_FOREIGN_FPSTATE always set for kernel threads, this patch
      ensures that no extra context save work is added for kernel
      threads, and eliminates the redundant context saving that may
      currently occur for kernel threads that have acquired an mm via
      use_mm().
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Reviewed-by: NChristoffer Dall <christoffer.dall@arm.com>
      Cc: Catalin Marinas <catalin.marinas@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      df3fb968
    • D
      arm64: fpsimd: Avoid FPSIMD context leakage for the init task · 66e48a0d
      Dave Martin 提交于
      The init task is started with thread_flags equal to 0, which means
      that TIF_FOREIGN_FPSTATE is initially clear.
      
      It is theoretically possible (if unlikely) that the init task could
      reach userspace without ever being scheduled out.  If this occurs,
      data left in the FPSIMD registers by the kernel could be exposed.
      
      This patch fixes this anomaly by ensuring that the init task's
      initial TIF_FOREIGN_FPSTATE is set.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Fixes: 005f78cd ("arm64: defer reloading a task's FPSIMD state to userland resume")
      Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      66e48a0d
    • D
      arm64: fpsimd: Generalise context saving for non-task contexts · d1797615
      Dave Martin 提交于
      In preparation for allowing non-task (i.e., KVM vcpu) FPSIMD
      contexts to be handled by the fpsimd common code, this patch adapts
      task_fpsimd_save() to save back the currently loaded context,
      removing the explicit dependency on current.
      
      The relevant storage to write back to in memory is now found by
      examining the fpsimd_last_state percpu struct.
      
      fpsimd_save() does nothing unless TIF_FOREIGN_FPSTATE is clear, and
      fpsimd_last_state is updated under local_bh_disable() or
      local_irq_disable() everywhere that TIF_FOREIGN_FPSTATE is cleared:
      thus, fpsimd_save() will write back to the correct storage for the
      loaded context.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      d1797615
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      KVM: arm64: Convert lazy FPSIMD context switch trap to C · ceda9fff
      Dave Martin 提交于
      To make the lazy FPSIMD context switch trap code easier to hack on,
      this patch converts it to C.
      
      This is not amazingly efficient, but the trap should typically only
      be taken once per host context switch.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      ceda9fff
    • C
      KVM: arm/arm64: Introduce kvm_arch_vcpu_run_pid_change · bd2a6394
      Christoffer Dall 提交于
      KVM/ARM differs from other architectures in having to maintain an
      additional virtual address space from that of the host and the
      guest, because we split the execution of KVM across both EL1 and
      EL2.
      
      This results in a need to explicitly map data structures into EL2
      (hyp) which are accessed from the hyp code.  As we are about to be
      more clever with our FPSIMD handling on arm64, which stores data in
      the task struct and uses thread_info flags, we will have to map
      parts of the currently executing task struct into the EL2 virtual
      address space.
      
      However, we don't want to do this on every KVM_RUN, because it is a
      fairly expensive operation to walk the page tables, and the common
      execution mode is to map a single thread to a VCPU.  By introducing
      a hook that architectures can select with
      HAVE_KVM_VCPU_RUN_PID_CHANGE, we do not introduce overhead for
      other architectures, but have a simple way to only map the data we
      need when required for arm64.
      
      This patch introduces the framework only, and wires it up in the
      arm/arm64 KVM common code.
      
      No functional change.
      Signed-off-by: NChristoffer Dall <christoffer.dall@linaro.org>
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      bd2a6394
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      arm64: Use update{,_tsk}_thread_flag() · 09d1223a
      Dave Martin 提交于
      This patch uses the new update_thread_flag() helpers to simplify a
      couple of if () set; else clear; constructs.
      
      No functional change.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      09d1223a
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      thread_info: Add update_thread_flag() helpers · 93ee37c2
      Dave Martin 提交于
      There are a number of bits of code sprinkled around the kernel to
      set a thread flag if a certain condition is true, and clear it
      otherwise.
      
      To help make those call sites terser and less cumbersome, this
      patch adds a new family of thread flag manipulators
      
      	update*_thread_flag([...,] flag, cond)
      
      which do the equivalent of:
      
      	if (cond)
      		set*_thread_flag([...,] flag);
      	else
      		clear*_thread_flag([...,] flag);
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Acked-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
      Acked-by: NMarc Zyngier <marc.zyngier@arm.com>
      Acked-by: NCatalin Marinas <catalin.marinas@arm.com>
      Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      93ee37c2
    • D
      arm64: fpsimd: Fix TIF_FOREIGN_FPSTATE after invalidating cpu regs · d8ad71fa
      Dave Martin 提交于
      fpsimd_last_state.st is set to NULL as a way of indicating that
      current's FPSIMD registers are no longer loaded in the cpu.  In
      particular, this is done when the kernel temporarily uses or
      clobbers the FPSIMD registers for its own purposes, as in CPU PM or
      kernel-mode NEON, resulting in them being populated with garbage
      data not belonging to a task.
      
      Commit 17eed27b ("arm64/sve: KVM: Prevent guests from using
      SVE") factors this operation out as a new helper
      fpsimd_flush_cpu_state() to make it clearer what is being done
      here, and on SVE systems this helper is now used, via
      kvm_fpsimd_flush_cpu_state(), to invalidate the registers after KVM
      has run a vcpu.  The reason for this is that KVM does not yet
      understand how to restore the full host SVE registers itself after
      loading the guest FPSIMD context into them.
      
      This exposes a particular problem: if fpsimd_last_state.st is set
      to NULL without also setting TIF_FOREIGN_FPSTATE, the kernel may
      continue to think that current's FPSIMD registers are live even
      though they have actually been clobbered.
      
      Prior to the aforementioned commit, the only path where
      fpsimd_last_state.st is set to NULL without setting
      TIF_FOREIGN_FPSTATE is when kernel_neon_begin() is called by a
      kernel thread (where current->mm can be NULL).  This does not
      matter, because the only harm is that at context-switch time
      fpsimd_thread_switch() may unnecessarily save the FPSIMD registers
      back to current's thread_struct (even though kernel threads are not
      considered to have any FPSIMD context of their own and the
      registers will never be reloaded).
      
      Note that although CPU_PM_ENTER lacks the TIF_FOREIGN_FPSTATE
      setting, every CPU passing through that path must subsequently pass
      through CPU_PM_EXIT before it can re-enter the kernel proper.
      CPU_PM_EXIT sets the flag.
      
      The sve_flush_cpu_state() function added by commit 17eed27b
      also lacks the proper maintenance of TIF_FOREIGN_FPSTATE.  This may
      cause the bits of a host task's SVE registers that do not alias the
      FPSIMD register file to spontaneously appear zeroed if a KVM vcpu
      runs in the same task in the meantime.  Although this effect is
      hidden by the fact that the non-FPSIMD bits of the SVE registers
      are zeroed by a syscall anyway, it is doubtless a bad idea to rely
      on these different code paths interacting correctly under future
      maintenance.
      
      This patch makes TIF_FOREIGN_FPSTATE an unconditional side-effect
      of fpsimd_flush_cpu_state(), and removes the set_thread_flag()
      calls that become redundant as a result.  This ensures that
      TIF_FOREIGN_FPSTATE cannot remain clear if the FPSIMD state in the
      FPSIMD registers is invalid.
      Signed-off-by: NDave Martin <Dave.Martin@arm.com>
      Reviewed-by: NChristoffer Dall <christoffer.dall@arm.com>
      Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
      Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      d8ad71fa
  2. 20 5月, 2018 1 次提交
    • M
      arm64: KVM: Use lm_alias() for kvm_ksym_ref() · 46c4a30b
      Mark Rutland 提交于
      For historical reasons, we open-code lm_alias() in kvm_ksym_ref().
      
      Let's use lm_alias() to avoid duplication and make things clearer.
      
      As we have to pull this from <linux/mm.h> (which is not safe for
      inclusion in assembly), we may as well move the kvm_ksym_ref()
      definition into the existing !__ASSEMBLY__ block.
      Signed-off-by: NMark Rutland <mark.rutland@arm.com>
      Cc: Christoffer Dall <christoffer.dall@arm.com>
      Cc: Marc Zyngier <marc.zyngier@arm.com>
      Cc: kvmarm@lists.cs.columbia.edu
      Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
      46c4a30b
  3. 07 5月, 2018 1 次提交
  4. 06 5月, 2018 9 次提交
    • L
      Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm · 701e39d0
      Linus Torvalds 提交于
      Pll KVM fixes from Radim Krčmář:
       "ARM:
         - Fix proxying of GICv2 CPU interface accesses
         - Fix crash when switching to BE
         - Track source vcpu git GICv2 SGIs
         - Fix an outdated bit of documentation
      
        x86:
         - Speed up injection of expired timers (for stable)"
      
      * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
        KVM: x86: remove APIC Timer periodic/oneshot spikes
        arm64: vgic-v2: Fix proxying of cpuif access
        KVM: arm/arm64: vgic_init: Cleanup reference to process_maintenance
        KVM: arm64: Fix order of vcpu_write_sys_reg() arguments
        KVM: arm/arm64: vgic: Fix source vcpu issues for GICv2 SGI
      701e39d0
    • L
      Merge tag 'iommu-fixes-v4.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu · 772d4f84
      Linus Torvalds 提交于
      Pull iommu fixes from Joerg Roedel:
      
       - fix a compile warning in the AMD IOMMU driver with irq remapping
         disabled
      
       - fix for VT-d interrupt remapping and invalidation size (caused a
         BUG_ON when trying to invalidate more than 4GB)
      
       - build fix and a regression fix for broken graphics with old DTS for
         the rockchip iommu driver
      
       - a revert in the PCI window reservation code which fixes a regression
         with VFIO.
      
      * tag 'iommu-fixes-v4.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu:
        iommu: rockchip: fix building without CONFIG_OF
        iommu/vt-d: Use WARN_ON_ONCE instead of BUG_ON in qi_flush_dev_iotlb()
        iommu/vt-d: fix shift-out-of-bounds in bug checking
        iommu/dma: Move PCI window region reservation back into dma specific path.
        iommu/rockchip: Make clock handling optional
        iommu/amd: Hide unused iommu_table_lock
        iommu/vt-d: Fix usage of force parameter in intel_ir_reconfigure_irte()
      772d4f84
    • L
      Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 9c48eb6a
      Linus Torvalds 提交于
      Pull x86 fix from Thomas Gleixner:
       "Unbreak the CPUID CPUID_8000_0008_EBX reload which got dropped when
        the evaluation of physical and virtual bits which uses the same CPUID
        leaf was moved out of get_cpu_cap()"
      
      * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        x86/cpu: Restore CPUID_8000_0008_EBX reload
      9c48eb6a
    • L
      Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · fe282c60
      Linus Torvalds 提交于
      Pull clocksource fixes from Thomas Gleixner:
       "The recent addition of the early TSC clocksource breaks on machines
        which have an unstable TSC because in case that TSC is disabled, then
        the clocksource selection logic falls back to the early TSC which is
        obviously bogus.
      
        That also unearthed a few robustness issues in the clocksource
        derating code which are addressed as well"
      
      * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        clocksource: Rework stale comment
        clocksource: Consistent de-rate when marking unstable
        x86/tsc: Fix mark_tsc_unstable()
        clocksource: Initialize cs->wd_list
        clocksource: Allow clocksource_mark_unstable() on unregistered clocksources
        x86/tsc: Always unregister clocksource_tsc_early
      fe282c60
    • L
      Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip · 03b5f0c1
      Linus Torvalds 提交于
      Pull irq fix from Thomas Gleixner:
       "A single fix to prevent false positives in the spurious interrupt
        detector when more than a single demultiplex register is evaluated in
        the Qualcom irq combiner driver"
      
      * 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
        irqchip/qcom: Fix check for spurious interrupts
      03b5f0c1
    • L
      Merge tag 'platform-drivers-x86-v4.17-2' of git://git.infradead.org/linux-platform-drivers-x86 · ee946c36
      Linus Torvalds 提交于
      Pull x86 platform driver fixes from Darren Hart:
      
       - We missed a case in the Dell config dependencies resulting in a
         possible bad configuration, resolve it by giving up on trying to keep
         DELL_LAPTOP visible in the menu and make it depend on DELL_SMBIOS.
      
       - Fix a null pointer dereference at module unload for the asus-wireless
         driver.
      
      * tag 'platform-drivers-x86-v4.17-2' of git://git.infradead.org/linux-platform-drivers-x86:
        platform/x86: Kconfig: Fix dell-laptop dependency chain.
        platform/x86: asus-wireless: Fix NULL pointer dereference
      ee946c36
    • L
      Merge tag 'usb-4.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb · 8e95cb33
      Linus Torvalds 提交于
      Pull USB fixes from Greg KH:
       "Here are some USB driver fixes for 4.17-rc4.
      
        The majority of them are some USB gadget fixes that missed my last
        pull request. The "largest" patch in here is a fix for the old visor
        driver that syzbot found 6 months or so ago and I finally remembered
        to fix it.
      
        All of these have been in linux-next with no reported issues"
      
      * tag 'usb-4.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
        Revert "usb: host: ehci: Use dma_pool_zalloc()"
        usb: typec: tps6598x: handle block reads separately with plain-I2C adapters
        usb: typec: tcpm: Release the role mux when exiting
        USB: Accept bulk endpoints with 1024-byte maxpacket
        xhci: Fix use-after-free in xhci_free_virt_device
        USB: serial: visor: handle potential invalid device configuration
        USB: serial: option: adding support for ublox R410M
        usb: musb: trace: fix NULL pointer dereference in musb_g_tx()
        usb: musb: host: fix potential NULL pointer dereference
        usb: gadget: composite Allow for larger configuration descriptors
        usb: dwc3: gadget: Fix list_del corruption in dwc3_ep_dequeue
        usb: dwc3: gadget: dwc3_gadget_del_and_unmap_request() can be static
        usb: dwc2: pci: Fix error return code in dwc2_pci_probe()
        usb: dwc2: WA for Full speed ISOC IN in DDMA mode.
        usb: dwc2: dwc2_vbus_supply_init: fix error check
        usb: gadget: f_phonet: fix pn_net_xmit()'s return type
      8e95cb33
    • A
      KVM: x86: remove APIC Timer periodic/oneshot spikes · ecf08dad
      Anthoine Bourgeois 提交于
      Since the commit "8003c9ae: add APIC Timer periodic/oneshot mode VMX
      preemption timer support", a Windows 10 guest has some erratic timer
      spikes.
      
      Here the results on a 150000 times 1ms timer without any load:
      	  Before 8003c9ae | After 8003c9ae
      Max           1834us          |  86000us
      Mean          1100us          |   1021us
      Deviation       59us          |    149us
      Here the results on a 150000 times 1ms timer with a cpu-z stress test:
      	  Before 8003c9ae | After 8003c9ae
      Max          32000us          | 140000us
      Mean          1006us          |   1997us
      Deviation      140us          |  11095us
      
      The root cause of the problem is starting hrtimer with an expiry time
      already in the past can take more than 20 milliseconds to trigger the
      timer function.  It can be solved by forward such past timers
      immediately, rather than submitting them to hrtimer_start().
      In case the timer is periodic, update the target expiration and call
      hrtimer_start with it.
      
      v2: Check if the tsc deadline is already expired. Thank you Mika.
      v3: Execute the past timers immediately rather than submitting them to
      hrtimer_start().
      v4: Rearm the periodic timer with advance_periodic_target_expiration() a
      simpler version of set_target_expiration(). Thank you Paolo.
      
      Cc: Mika Penttilä <mika.penttila@nextfour.com>
      Cc: Wanpeng Li <kernellwp@gmail.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: stable@vger.kernel.org
      Signed-off-by: NAnthoine Bourgeois <anthoine.bourgeois@blade-group.com>
      8003c9ae ("KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer support")
      Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      ecf08dad
    • R
      Merge tag 'kvmarm-fixes-for-4.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm · f3351c60
      Radim Krčmář 提交于
      KVM/arm fixes for 4.17, take #2
      
      - Fix proxying of GICv2 CPU interface accesses
      - Fix crash when switching to BE
      - Track source vcpu git GICv2 SGIs
      - Fix an outdated bit of documentation
      f3351c60
  5. 05 5月, 2018 8 次提交
    • L
      Merge tag 'kbuild-fixes-v4.17' of... · c1c07416
      Linus Torvalds 提交于
      Merge tag 'kbuild-fixes-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
      
      Pull Kbuild fixes from Masahiro Yamada:
      
       - remove state comment in modpost
      
       - extend MAINTAINERS entry to cover modpost and more makefiles
      
       - fix missed building of SANCOV gcc-plugin
      
       - replace left-over 'bison' with $(YACC)
      
       - display short log when generating parer of genksyms
      
      * tag 'kbuild-fixes-v4.17' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
        genksyms: fix typo in parse.tab.{c,h} generation rules
        kbuild: replace hardcoded bison in cmd_bison_h with $(YACC)
        gcc-plugins: fix build condition of SANCOV plugin
        MAINTAINERS: Update Kbuild entry with a few paths
        modpost: delete stale comment
      c1c07416
    • L
      Merge tag 'clk-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux · 4a7a7729
      Linus Torvalds 提交于
      Pull clk fixes froom Stephen Boyd:
       "A handful of fixes for the stm32mp1 clk driver came in during the
        merge window for the driver that got merged in the merge window.
      
        Plus a warning fix for unused PM ops and a couple fixes for the meson
        clk driver clk names that went unnoticed with the regmap rework.
      
        There's also another fix in here for the mux rounding flag which
        wasn't doing what it said it did, but now it does"
      
      * tag 'clk-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
        clk: meson: meson8b: fix meson8b_cpu_clk parent clock name
        clk: meson: meson8b: fix meson8b_fclk_div3_div clock name
        clk: meson: drop meson_aoclk_gate_regmap_ops
        clk: meson: honor CLK_MUX_ROUND_CLOSEST in clk_regmap
        clk: honor CLK_MUX_ROUND_CLOSEST in generic clk mux
        clk: cs2000: mark resume function as __maybe_unused
        clk: stm32mp1: remove ck_apb_dbg clock
        clk: stm32mp1: set stgen_k clock as critical
        clk: stm32mp1: add missing tzc2 clock
        clk: stm32mp1: fix SAI3 & SAI4 clocks
        clk: stm32mp1: remove unused dfsdm_src[] const
        clk: stm32mp1: add missing static
      4a7a7729
    • L
      Merge tag 'rproc-v4.17-1' of git://github.com/andersson/remoteproc · f9331473
      Linus Torvalds 提交于
      Pull remoteproc and rpmsg fixes from Bjorn Andersson:
      
       - fix screw-up when reversing boolean for rproc_stop()
      
       - add missing OF node refcounting dereferences
      
       - add missing MODULE_ALIAS in rpmsg_char
      
      * tag 'rproc-v4.17-1' of git://github.com/andersson/remoteproc:
        rpmsg: added MODULE_ALIAS for rpmsg_char
        remoteproc: qcom: Fix potential device node leaks
        remoteproc: fix crashed parameter logic on stop call
      f9331473
    • L
      Merge tag 'drm-fixes-for-v4.17-rc4' of git://people.freedesktop.org/~airlied/linux · c12fd0fe
      Linus Torvalds 提交于
      Pull drm fixes from Dave Airlie:
       "vmwgfx, i915, vc4, vga dac fixes.
      
        This seems eerily quiet, so I expect it will explode next week or
        something.
      
        One i915 model firmware, two vmwgfx fixes, one vc4 fix and one bridge
        leak fix"
      
      * tag 'drm-fixes-for-v4.17-rc4' of git://people.freedesktop.org/~airlied/linux:
        drm/bridge: vga-dac: Fix edid memory leak
        drm/vc4: Make sure vc4_bo_{inc,dec}_usecnt() calls are balanced
        drm/i915/glk: Add MODULE_FIRMWARE for Geminilake
        drm/vmwgfx: Fix a buffer object leak
        drm/vmwgfx: Clean up fbdev modeset locking
      c12fd0fe
    • L
      Merge tag 'trace-v4.17-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace · 4b293907
      Linus Torvalds 提交于
      Pull tracing fixes from Steven Rostedt:
       "Some of the files in the tracing directory show file mode 0444 when
        they are writable by root. To fix the confusion, they should be 0644.
        Note, either case root can still write to them.
      
        Zhengyuan asked why I never applied that patch (the first one is from
        2014!). I simply forgot about it. /me lowers head in shame"
      
      * tag 'trace-v4.17-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
        tracing: Fix the file mode of stack tracer
        ftrace: Have set_graph_* files have normal file modes
      4b293907
    • L
      Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma · eb4f959b
      Linus Torvalds 提交于
      Pull rdma fixes from Doug Ledford:
       "This is our first pull request of the rc cycle. It's not that it's
        been overly quiet, we were just waiting on a few things before sending
        this off.
      
        For instance, the 6 patch series from Intel for the hfi1 driver had
        actually been pulled in on Tuesday for a Wednesday pull request, only
        to have Jason notice something I missed, so we held off for some
        testing, and then on Thursday had to respin the series because the
        very first patch needed a minor fix (unnecessary cast is all).
      
        There is a sizable hns patch series in here, as well as a reasonably
        largish hfi1 patch series, then all of the lines of uapi updates are
        just the change to the new official Linux-OpenIB SPDX tag (a bunch of
        our files had what amounts to a BSD-2-Clause + MIT Warranty statement
        as their license as a result of the initial code submission years ago,
        and the SPDX folks decided it was unique enough to warrant a unique
        tag), then the typical mlx4 and mlx5 updates, and finally some cxgb4
        and core/cache/cma updates to round out the bunch.
      
        None of it was overly large by itself, but in the 2 1/2 weeks we've
        been collecting patches, it has added up :-/.
      
        As best I can tell, it's been through 0day (I got a notice about my
        last for-next push, but not for my for-rc push, but Jason seems to
        think that failure messages are prioritized and success messages not
        so much). It's also been through linux-next. And yes, we did notice in
        the context portion of the CMA query gid fix patch that there is a
        dubious BUG_ON() in the code, and have plans to audit our BUG_ON usage
        and remove it anywhere we can.
      
        Summary:
      
         - Various build fixes (USER_ACCESS=m and ADDR_TRANS turned off)
      
         - SPDX license tag cleanups (new tag Linux-OpenIB)
      
         - RoCE GID fixes related to default GIDs
      
         - Various fixes to: cxgb4, uverbs, cma, iwpm, rxe, hns (big batch),
           mlx4, mlx5, and hfi1 (medium batch)"
      
      * tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: (52 commits)
        RDMA/cma: Do not query GID during QP state transition to RTR
        IB/mlx4: Fix integer overflow when calculating optimal MTT size
        IB/hfi1: Fix memory leak in exception path in get_irq_affinity()
        IB/{hfi1, rdmavt}: Fix memory leak in hfi1_alloc_devdata() upon failure
        IB/hfi1: Fix NULL pointer dereference when invalid num_vls is used
        IB/hfi1: Fix loss of BECN with AHG
        IB/hfi1 Use correct type for num_user_context
        IB/hfi1: Fix handling of FECN marked multicast packet
        IB/core: Make ib_mad_client_id atomic
        iw_cxgb4: Atomically flush per QP HW CQEs
        IB/uverbs: Fix kernel crash during MR deregistration flow
        IB/uverbs: Prevent reregistration of DM_MR to regular MR
        RDMA/mlx4: Add missed RSS hash inner header flag
        RDMA/hns: Fix a couple misspellings
        RDMA/hns: Submit bad wr
        RDMA/hns: Update assignment method for owner field of send wqe
        RDMA/hns: Adjust the order of cleanup hem table
        RDMA/hns: Only assign dqpn if IB_QP_PATH_DEST_QPN bit is set
        RDMA/hns: Remove some unnecessary attr_mask judgement
        RDMA/hns: Only assign mtu if IB_QP_PATH_MTU bit is set
        ...
      eb4f959b
    • L
      Merge tag 'for-linus-20180504' of git://git.kernel.dk/linux-block · 2f50037a
      Linus Torvalds 提交于
      Pull block fixes from Jens Axboe:
       "A collection of fixes that should to into this release. This contains:
      
         - Set of bcache fixes from Coly, fixing regression in patches that
           went into this series.
      
         - Set of NVMe fixes by way of Keith.
      
         - Set of bdi related fixes, one from Jan and two from Tetsuo Handa,
           fixing various issues around device addition/removal.
      
         - Two block inflight fixes from Omar, fixing issues around the
           transition to using tags for blk-mq inflight accounting that we
           did a few releases ago"
      
      * tag 'for-linus-20180504' of git://git.kernel.dk/linux-block:
        bdi: Fix oops in wb_workfn()
        nvmet: switch loopback target state to connecting when resetting
        nvme/multipath: Fix multipath disabled naming collisions
        nvme/multipath: Disable runtime writable enabling parameter
        nvme: Set integrity flag for user passthrough commands
        nvme: fix potential memory leak in option parsing
        bdi: Fix use after free bug in debugfs_remove()
        bdi: wake up concurrent wb_shutdown() callers.
        bcache: use pr_info() to inform duplicated CACHE_SET_IO_DISABLE set
        bcache: set dc->io_disable to true in conditional_stop_bcache_device()
        bcache: add wait_for_kthread_stop() in bch_allocator_thread()
        bcache: count backing device I/O error for writeback I/O
        bcache: set CACHE_SET_IO_DISABLE in bch_cached_dev_error()
        bcache: store disk name in struct cache and struct cached_dev
        blk-mq: fix sysfs inflight counter
        blk-mq: count allocated but not started requests in iostats inflight
      2f50037a
    • L
      Merge tag 'xfs-4.17-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux · 2e171ffc
      Linus Torvalds 提交于
      Pull xfs fixes from Darrick Wong:
       "I've got one more bug fix for xfs for 4.17-rc4, which caps the amount
        of data we try to handle in one dedupe request so that userspace can't
        livelock the kernel.
      
        This series has been run through a full xfstests run during the week
        and through a quick xfstests run against this morning's master, with
        no ajor failures reported.
      
        Summary:
      
        - Cap the maximum length of a deduplication request at MAX_RW_COUNT/2
          to avoid kernel livelock due to excessively large IO requests"
      
      * tag 'xfs-4.17-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
        xfs: cap the length of deduplication requests
      2e171ffc