Add a section to document all the different ways in which the KVM API sucks.

I am sure there are way more, give people a place to vent so that userspace
authors are aware.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220322110712.222449-4-pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add a file to document all the different ways in which the virtual CPU
emulation is imperfect.  Include an example to show how to document
such errata.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Reviewed-by: NOliver Upton <oupton@google.com>
Message-Id: <20220322110712.222449-3-pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

ARM already has an arm/ subdirectory, but s390 and x86 do not even though
they have a relatively large number of files specific to them.  Create
new directories in Documentation/virt/kvm for these two architectures
as well.

While at it, group the API documentation and the developer documentation
in the table of contents.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220322110712.222449-2-pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

kvm->mn_invalidate_lock and kvm->slots_arch_lock were not included in the
documentation, add them.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220322110720.222499-3-pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Separate the various locks clearly, and include the new names of blocked_vcpu_on_cpu_lock
and blocked_vcpu_on_cpu.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220322110720.222499-2-pbonzini@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Clang warns:

  arch/x86/kvm/cpuid.c:739:2: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
          default:
          ^
  arch/x86/kvm/cpuid.c:739:2: note: insert 'break;' to avoid fall-through
          default:
          ^
          break;
  1 error generated.

Clang is a little more pedantic than GCC, which does not warn when
falling through to a case that is just break or return. Clang's version
is more in line with the kernel's own stance in deprecated.rst, which
states that all switch/case blocks must end in either break,
fallthrough, continue, goto, or return. Add the missing break to silence
the warning.

Fixes: f144c49e ("KVM: x86: synthesize CPUID leaf 0x80000021h if useful")
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NNathan Chancellor <nathan@kernel.org>
Message-Id: <20220322152906.112164-1-nathan@kernel.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This reverts commit 3d3aab1b.

Now that the KVM module's lifetime is tied to kvm.users_count, there is
no need to also tie it's lifetime to the lifetime of the VM and vCPU
file descriptors.
Suggested-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Message-Id: <20220303183328.1499189-3-dmatlack@google.com>
Reviewed-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Tie the lifetime the KVM module to the lifetime of each VM via
kvm.users_count. This way anything that grabs a reference to the VM via
kvm_get_kvm() cannot accidentally outlive the KVM module.

Prior to this commit, the lifetime of the KVM module was tied to the
lifetime of /dev/kvm file descriptors, VM file descriptors, and vCPU
file descriptors by their respective file_operations "owner" field.
This approach is insufficient because references grabbed via
kvm_get_kvm() do not prevent closing any of the aforementioned file
descriptors.

This fixes a long standing theoretical bug in KVM that at least affects
async page faults. kvm_setup_async_pf() grabs a reference via
kvm_get_kvm(), and drops it in an asynchronous work callback. Nothing
prevents the VM file descriptor from being closed and the KVM module
from being unloaded before this callback runs.

Fixes: af585b92 ("KVM: Halt vcpu if page it tries to access is swapped out")
Fixes: 3d3aab1b ("KVM: set owner of cpu and vm file operations")
Cc: stable@vger.kernel.org
Suggested-by: NBen Gardon <bgardon@google.com>
[ Based on a patch from Ben implemented for Google's kernel. ]
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Message-Id: <20220303183328.1499189-2-dmatlack@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Instead of using array_size, use a function that takes care of the
multiplication.  While at it, switch to kvcalloc since this allocation
should not be very large.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

KVM_CAP_DISABLE_QUIRKS is irrevocably broken. The capability does not
advertise the set of quirks which may be disabled to userspace, so it is
impossible to predict the behavior of KVM. Worse yet,
KVM_CAP_DISABLE_QUIRKS will tolerate any value for cap->args[0], meaning
it fails to reject attempts to set invalid quirk bits.

The only valid workaround for the quirky quirks API is to add a new CAP.
Actually advertise the set of quirks that can be disabled to userspace
so it can predict KVM's behavior. Reject values for cap->args[0] that
contain invalid bits.

Finally, add documentation for the new capability and describe the
existing quirks.
Signed-off-by: NOliver Upton <oupton@google.com>
Message-Id: <20220301060351.442881-5-oupton@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Non constant TSC is a nightmare on bare metal already, but with
virtualization it becomes a complete disaster because the workarounds
are horrible latency wise. That's also a preliminary for running RT in
a guest on top of a RT host.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Message-Id: <Yh5eJSG19S2sjZfy@linutronix.de>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Guests X86_BUG_NULL_SEG if and only if the host has them.  Use the info
from static_cpu_has_bug to form the 0x80000021 CPUID leaf that was
defined for Zen3.  Userspace can then set the bit even on older CPUs
that do not have the bug, such as Zen2.

Do the same for X86_FEATURE_LFENCE_RDTSC as well, since various processors
have had very different ways of detecting it and not all of them are
available to userspace.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

CPUID leaf 0x80000021 defines some features (or lack of bugs) of AMD
processors.  Expose the ones that make sense via KVM_GET_SUPPORTED_CPUID.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

KVM_X86_OP_OPTIONAL_RET0 can only be used with 32-bit return values on 32-bit
systems, because unsigned long is only 32-bits wide there and 64-bit values
are returned in edx:eax.
Reported-by: NMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: NMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This reverts commit cf3e2642.

Multi-vCPU Hyper-V guests started crashing randomly on boot with the
latest kvm/queue and the problem can be bisected the problem to this
particular patch. Basically, I'm not able to boot e.g. 16-vCPU guest
successfully anymore. Both Intel and AMD seem to be affected. Reverting
the commit saves the day.
Reported-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Since "KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn_range()"
is going to be reverted, it's not going to be true anymore that
the zap-page flow does not free any 'struct kvm_mmu_page'.  Introduce
an early flush before tdp_mmu_zap_leafs() returns, to preserve
bisectability.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

KVM/arm64 updates for 5.18

- Proper emulation of the OSLock feature of the debug architecture

- Scalibility improvements for the MMU lock when dirty logging is on

- New VMID allocator, which will eventually help with SVA in VMs

- Better support for PMUs in heterogenous systems

- PSCI 1.1 support, enabling support for SYSTEM_RESET2

- Implement CONFIG_DEBUG_LIST at EL2

- Make CONFIG_ARM64_ERRATUM_2077057 default y

- Reduce the overhead of VM exit when no interrupt is pending

- Remove traces of 32bit ARM host support from the documentation

- Updated vgic selftests

- Various cleanups, doc updates and spelling fixes

Various spelling mistakes in comments.
Detected with the help of Coccinelle.
Signed-off-by: NJulia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220318103729.157574-24-Julia.Lawall@inria.fr

We currently deal with a set of booleans for VM features,
while they could be better represented as set of flags
contained in an unsigned long, similarily to what we are
doing on the CPU side.
Signed-off-by: NMarc Zyngier <maz@kernel.org>
[Oliver: Flag-ify the 'ran_once' boolean]
Signed-off-by: NOliver Upton <oupton@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220311174001.605719-2-oupton@google.com

KVM/riscv changes for 5.18

- Prevent KVM_COMPAT from being selected
- Refine __kvm_riscv_switch_to() implementation
- RISC-V SBI v0.3 support

Merge tag 'kvm-s390-next-5.18-2' of https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into HEAD

KVM: s390: Fix, test and feature for 5.18 part 2

- memop selftest
- fix SCK locking
- adapter interruptions virtualization for secure guests

Test that errors occur if key protection disallows access, including
tests for storage and fetch protection override. Perform tests for both
logical vcpu and absolute vm ioctls.
Also extend the existing tests to the vm ioctl.
Signed-off-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220308125841.3271721-6-scgl@linux.ibm.comSigned-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>

Do not just test the actual copy, but also that success is indicated
when using the check only flag.
Add copy test with storage key checking enabled, including tests for
storage and fetch protection override.
These test cover both logical vcpu ioctls as well as absolute vm ioctls.
Signed-off-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220308125841.3271721-5-scgl@linux.ibm.comSigned-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>

The stages synchronize guest and host execution.
This helps the reader and constraits the execution of the test -- if the
observed staging differs from the expected the test fails.
Signed-off-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220308125841.3271721-4-scgl@linux.ibm.comSigned-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>

In order to achieve good test coverage we need to be able to invoke the
MEM_OP ioctl with all possible parametrizations.
However, for a given test, we want to be concise and not specify a long
list of default values for parameters not relevant for the test, so the
readers attention is not needlessly diverted.
Add a macro that enables this and convert the existing test to use it.
The macro emulates named arguments and hides some of the ioctl's
redundancy, e.g. sets the key flag if an access key is specified.
Signed-off-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220308125841.3271721-3-scgl@linux.ibm.comSigned-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>

Split success case/copy test from error test, making them independent.
This means they do not share state and are easier to understand.
Also, new test can be added in the same manner without affecting the old
ones. In order to make that simpler, introduce functionality for the
setup of commonly used variables.
Signed-off-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220308125841.3271721-2-scgl@linux.ibm.comSigned-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>

When handling the SCK instruction, the kvm lock is taken, even though
the vcpu lock is already being held. The normal locking order is kvm
lock first and then vcpu lock. This is can (and in some circumstances
does) lead to deadlocks.

The function kvm_s390_set_tod_clock is called both by the SCK handler
and by some IOCTLs to set the clock. The IOCTLs will not hold the vcpu
lock, so they can safely take the kvm lock. The SCK handler holds the
vcpu lock, but will also somehow need to acquire the kvm lock without
relinquishing the vcpu lock.

The solution is to factor out the code to set the clock, and provide
two wrappers. One is called like the original function and does the
locking, the other is called kvm_s390_try_set_tod_clock and uses
trylock to try to acquire the kvm lock. This new wrapper is then used
in the SCK handler. If locking fails, -EAGAIN is returned, which is
eventually propagated to userspace, thus also freeing the vcpu lock and
allowing for forward progress.

This is not the most efficient or elegant way to solve this issue, but
the SCK instruction is deprecated and its performance is not critical.

The goal of this patch is just to provide a simple but correct way to
fix the bug.

Fixes: 6a3f95a6 ("KVM: s390: Intercept SCK instruction")
Signed-off-by: NClaudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: NChristian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: NJanis Schoetterl-Glausch <scgl@linux.ibm.com>
Link: https://lore.kernel.org/r/20220301143340.111129-1-imbrenda@linux.ibm.com
Cc: stable@vger.kernel.org
Signed-off-by: NChristian Borntraeger <borntraeger@linux.ibm.com>

The SBI v0.3 specification extends SBI HSM extension by adding SBI HSM
suspend call and related HART states. This patch extends the KVM RISC-V
HSM implementation to provide KVM guest a minimal SBI HSM suspend call
which is equivalent to a WFI instruction.
Signed-off-by: NAnup Patel <apatel@ventanamicro.com>
Reviewed-by: NAtish Patra <atishp@rivosinc.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

The wait for interrupt (WFI) instruction emulation can share the VCPU
halt logic with SBI HSM suspend emulation so this patch adds a common
kvm_riscv_vcpu_wfi() function for this purpose.
Signed-off-by: NAnup Patel <apatel@ventanamicro.com>
Reviewed-by: NAtish Patra <atishp@rivosinc.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

We add defines related to SBI HSM suspend call and also update HSM states
naming as-per the latest SBI specification.
Signed-off-by: NAnup Patel <apatel@ventanamicro.com>
Reviewed-by: NAtish Patra <atishp@rivosinc.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

The SBI v0.3 specification defines SRST (System Reset) extension which
provides a standard poweroff and reboot interface. This patch implements
SRST extension for the KVM Guest.
Signed-off-by: NAnup Patel <apatel@ventanamicro.com>
Reviewed-by: NAtish Patra <atishp@rivosinc.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

We rename kvm_sbi_system_shutdown() to kvm_riscv_vcpu_sbi_system_reset()
and move it to vcpu_sbi.c so that it can be shared by SBI v0.1 shutdown
and SBI v0.3 SRST extension.
Signed-off-by: NAnup Patel <apatel@ventanamicro.com>
Reviewed-by: NAtish Patra <atishp@rivosinc.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

We upgrade SBI spec version implemented by KVM RISC-V to v0.3 so
that Guest kernel can probe and use SBI extensions added by the
SBI v0.3 specification.
Signed-off-by: NAnup Patel <apatel@ventanamicro.com>
Reviewed-by: NAtish Patra <atishp@rivosinc.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

Kernel uses __kvm_riscv_switch_to() and __kvm_switch_return() to switch
the context of host kernel and guest kernel. Several CSRs belonging to the
context will be read and written during the context switch. To ensure
atomic read-modify-write control of CSR and ordering of CSR accesses, some
hardware blocks flush the pipeline when writing a CSR. In this
circumstance, grouping CSR executions together as much as possible can
reduce the performance impact of the pipeline. Therefore, this commit
reorders the CSR instructions to enhance the context switch performance..
Signed-off-by: NVincent Chen <vincent.chen@sifive.com>
Suggested-by: NHsinyi Lee <hsinyi.lee@sifive.com>
Suggested-by: NFu-Ching Yang <fu-ching.yang@sifive.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

Current riscv doesn't support the 32bit KVM API. Let's make it
clear by not selecting KVM_COMPAT.
Signed-off-by: NGuo Ren <guoren@linux.alibaba.com>
Signed-off-by: NGuo Ren <guoren@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Anup Patel <anup@brainfault.org>
Reviewed-by: NAnup Patel <anup@brainfault.org>
Signed-off-by: NAnup Patel <anup@brainfault.org>

Eliminate the following coccicheck warning:
./arch/riscv/kvm/vcpu_sbi_v01.c:117:2-3: Unneeded semicolon
Reported-by: NAbaci Robot <abaci@linux.alibaba.com>
Signed-off-by: NYang Li <yang.lee@linux.alibaba.com>
Signed-off-by: NAnup Patel <anup@brainfault.org>

* kvm-arm64/psci-1.1:
  : .
  : Limited PSCI-1.1 support from Will Deacon:
  :
  : This small series exposes the PSCI SYSTEM_RESET2 call to guests, which
  : allows the propagation of a "reset_type" and a "cookie" back to the VMM.
  : Although Linux guests only ever pass 0 for the type ("SYSTEM_WARM_RESET"),
  : the vendor-defined range can be used by a bootloader to provide additional
  : information about the reset, such as an error code.
  : .
  KVM: arm64: Really propagate PSCI SYSTEM_RESET2 arguments to userspace
Signed-off-by: NMarc Zyngier <maz@kernel.org>

Commit d43583b8 ("KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the
guest") hooked up the SYSTEM_RESET2 PSCI call for guests but failed to
preserve its arguments for userspace, instead overwriting them with
zeroes via smccc_set_retval(). As Linux only passes zeroes for these
arguments, this appeared to be working for Linux guests. Oh well.

Don't call smccc_set_retval() for a SYSTEM_RESET2 heading to userspace
and instead set X0 (and only X0) explicitly to PSCI_RET_INTERNAL_FAILURE
just in case the vCPU re-enters the guest.

Fixes: d43583b8 ("KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the guest")
Reported-by: NAndrew Walbran <qwandor@google.com>
Signed-off-by: NWill Deacon <will@kernel.org>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220309181308.982-1-will@kernel.org

* kvm-arm64/misc-5.18:
  : .
  : Misc fixes for KVM/arm64 5.18:
  :
  : - Drop unused kvm parameter to kvm_psci_version()
  :
  : - Implement CONFIG_DEBUG_LIST at EL2
  :
  : - Make CONFIG_ARM64_ERRATUM_2077057 default y
  :
  : - Only do the interrupt dance if we have exited because of an interrupt
  :
  : - Remove traces of 32bit ARM host support from the documentation
  : .
  Documentation: KVM: Update documentation to indicate KVM is arm64-only
  KVM: arm64: Only open the interrupt window on exit due to an interrupt
  KVM: arm64: Enable Cortex-A510 erratum 2077057 by default
Signed-off-by: NMarc Zyngier <maz@kernel.org>

KVM support for 32-bit ARM hosts (KVM/arm) has been removed from the
kernel since commit 541ad015 ("arm: Remove 32bit KVM host
support"). There still exists some remnants of the old architecture in
the KVM documentation.

Remove all traces of 32-bit host support from the documentation. Note
that AArch32 guests are still supported.
Suggested-by: NMarc Zyngier <maz@kernel.org>
Signed-off-by: NOliver Upton <oupton@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220308172856.2997250-1-oupton@google.com