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  1. 07 6月, 2017 5 次提交
  3. 01 6月, 2017 5 次提交
  5. 30 5月, 2017 2 次提交
  7. 27 5月, 2017 1 次提交
    • J
      KVM: x86: Fix virtual wire mode · 52b54190
      由 Jan H. Schönherr 提交于 
      Intel SDM says, that at most one LAPIC should be configured with ExtINT
delivery. KVM configures all LAPICs this way. This causes pic_unlock()
to kick the first available vCPU from the internal KVM data structures.
If this vCPU is not the BSP, but some not-yet-booted AP, the BSP may
never realize that there is an interrupt.

Fix that by enabling ExtINT delivery only for the BSP.

This allows booting a Linux guest without a TSC in the above situation.
Otherwise the BSP gets stuck in calibrate_delay_converge().
Signed-off-by: NJan H. Schönherr <jschoenh@amazon.de>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      52b54190
  9. 26 5月, 2017 2 次提交
    • J
      KVM: nVMX: Fix handling of lmsw instruction · e1d39b17
      由 Jan H. Schönherr 提交于 
      The decision whether or not to exit from L2 to L1 on an lmsw instruction is
based on bogus values: instead of using the information encoded within the
exit qualification, it uses the data also used for the mov-to-cr
instruction, which boils down to using whatever is in %eax at that point.

Use the correct values instead.

Without this fix, an L1 may not get notified when a 32-bit Linux L2
switches its secondary CPUs to protected mode; the L1 is only notified on
the next modification of CR0. This short time window poses a problem, when
there is some other reason to exit to L1 in between. Then, L2 will be
resumed in real mode and chaos ensues.
Signed-off-by: NJan H. Schönherr <jschoenh@amazon.de>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      e1d39b17
    • W
      KVM: X86: Fix preempt the preemption timer cancel · 5acc1ca4
      由 Wanpeng Li 提交于 
      Preemption can occur during cancel preemption timer, and there will be
inconsistent status in lapic, vmx and vmcs field.

          CPU0                    CPU1

  preemption timer vmexit
  handle_preemption_timer(vCPU0)
    kvm_lapic_expired_hv_timer
      vmx_cancel_hv_timer
        vmx->hv_deadline_tsc = -1
        vmcs_clear_bits
        /* hv_timer_in_use still true */
  sched_out
                           sched_in
                           kvm_arch_vcpu_load
                             vmx_set_hv_timer
                               write vmx->hv_deadline_tsc
                               vmcs_set_bits
                           /* back in kvm_lapic_expired_hv_timer */
                           hv_timer_in_use = false
                           ...
                           vmx_vcpu_run
                             vmx_arm_hv_run
                               write preemption timer deadline
                             spurious preemption timer vmexit
                               handle_preemption_timer(vCPU0)
                                 kvm_lapic_expired_hv_timer
                                   WARN_ON(!apic->lapic_timer.hv_timer_in_use);

This can be reproduced sporadically during boot of L2 on a
preemptible L1, causing a splat on L1.

 WARNING: CPU: 3 PID: 1952 at arch/x86/kvm/lapic.c:1529 kvm_lapic_expired_hv_timer+0xb5/0xd0 [kvm]
 CPU: 3 PID: 1952 Comm: qemu-system-x86 Not tainted 4.12.0-rc1+ #24 RIP: 0010:kvm_lapic_expired_hv_timer+0xb5/0xd0 [kvm]
  Call Trace:
  handle_preemption_timer+0xe/0x20 [kvm_intel]
  vmx_handle_exit+0xc9/0x15f0 [kvm_intel]
  ? lock_acquire+0xdb/0x250
  ? lock_acquire+0xdb/0x250
  ? kvm_arch_vcpu_ioctl_run+0xdf3/0x1ce0 [kvm]
  kvm_arch_vcpu_ioctl_run+0xe55/0x1ce0 [kvm]
  kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? __fget+0xf3/0x210
  do_vfs_ioctl+0xa4/0x700
  ? __fget+0x114/0x210
  SyS_ioctl+0x79/0x90
  do_syscall_64+0x8f/0x750
  ? trace_hardirqs_on_thunk+0x1a/0x1c
  entry_SYSCALL64_slow_path+0x25/0x25

This patch fixes it by disabling preemption while cancelling
preemption timer.  This way cancel_hv_timer is atomic with
respect to kvm_arch_vcpu_load.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      5acc1ca4
  11. 20 5月, 2017 5 次提交
    • R
      KVM: x86: prevent uninitialized variable warning in check_svme() · 92ceb767
      由 Radim Krčmář 提交于 
      get_msr() of MSR_EFER is currently always going to succeed, but static
checker doesn't see that far.

Don't complicate stuff and just use 0 for the fallback -- it means that
the feature is not present.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      92ceb767
    • R
      KVM: x86/vPMU: fix undefined shift in intel_pmu_refresh() · 34b0dadb
      由 Radim Krčmář 提交于 
      Static analysis noticed that pmu->nr_arch_gp_counters can be 32
(INTEL_PMC_MAX_GENERIC) and therefore cannot be used to shift 'int'.

I didn't add BUILD_BUG_ON for it as we have a better checker.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Fixes: 25462f7f ("KVM: x86/vPMU: Define kvm_pmu_ops to support vPMU function dispatch")
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      34b0dadb
    • R
      KVM: x86: zero base3 of unusable segments · f0367ee1
      由 Radim Krčmář 提交于 
      Static checker noticed that base3 could be used uninitialized if the
segment was not present (useable).  Random stack values probably would
not pass VMCS entry checks.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Fixes: 1aa36616 ("KVM: x86 emulator: consolidate segment accessors")
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      f0367ee1
    • W
      KVM: X86: Fix read out-of-bounds vulnerability in kvm pio emulation · cbfc6c91
      由 Wanpeng Li 提交于 
      Huawei folks reported a read out-of-bounds vulnerability in kvm pio emulation.

- "inb" instruction to access PIT Mod/Command register (ioport 0x43, write only,
  a read should be ignored) in guest can get a random number.
- "rep insb" instruction to access PIT register port 0x43 can control memcpy()
  in emulator_pio_in_emulated() to copy max 0x400 bytes but only read 1 bytes,
  which will disclose the unimportant kernel memory in host but no crash.

The similar test program below can reproduce the read out-of-bounds vulnerability:

void hexdump(void *mem, unsigned int len)
{
        unsigned int i, j;

        for(i = 0; i < len + ((len % HEXDUMP_COLS) ? (HEXDUMP_COLS - len % HEXDUMP_COLS) : 0); i++)
        {
                /* print offset */
                if(i % HEXDUMP_COLS == 0)
                {
                        printf("0x%06x: ", i);
                }

                /* print hex data */
                if(i < len)
                {
                        printf("%02x ", 0xFF & ((char*)mem)[i]);
                }
                else /* end of block, just aligning for ASCII dump */
                {
                        printf("   ");
                }

                /* print ASCII dump */
                if(i % HEXDUMP_COLS == (HEXDUMP_COLS - 1))
                {
                        for(j = i - (HEXDUMP_COLS - 1); j <= i; j++)
                        {
                                if(j >= len) /* end of block, not really printing */
                                {
                                        putchar(' ');
                                }
                                else if(isprint(((char*)mem)[j])) /* printable char */
                                {
                                        putchar(0xFF & ((char*)mem)[j]);
                                }
                                else /* other char */
                                {
                                        putchar('.');
                                }
                        }
                        putchar('\n');
                }
        }
}

int main(void)
{
	int i;
	if (iopl(3))
	{
		err(1, "set iopl unsuccessfully\n");
		return -1;
	}
	static char buf[0x40];

	/* test ioport 0x40,0x41,0x42,0x43,0x44,0x45 */

	memset(buf, 0xab, sizeof(buf));

	asm volatile("push %rdi;");
	asm volatile("mov %0, %%rdi;"::"q"(buf));

	asm volatile ("mov $0x40, %rdx;");
	asm volatile ("in %dx,%al;");
	asm volatile ("stosb;");

	asm volatile ("mov $0x41, %rdx;");
	asm volatile ("in %dx,%al;");
	asm volatile ("stosb;");

	asm volatile ("mov $0x42, %rdx;");
	asm volatile ("in %dx,%al;");
	asm volatile ("stosb;");

	asm volatile ("mov $0x43, %rdx;");
	asm volatile ("in %dx,%al;");
	asm volatile ("stosb;");

	asm volatile ("mov $0x44, %rdx;");
	asm volatile ("in %dx,%al;");
	asm volatile ("stosb;");

	asm volatile ("mov $0x45, %rdx;");
	asm volatile ("in %dx,%al;");
	asm volatile ("stosb;");

	asm volatile ("pop %rdi;");
	hexdump(buf, 0x40);

	printf("\n");

	/* ins port 0x40 */

	memset(buf, 0xab, sizeof(buf));

	asm volatile("push %rdi;");
	asm volatile("mov %0, %%rdi;"::"q"(buf));

	asm volatile ("mov $0x20, %rcx;");
	asm volatile ("mov $0x40, %rdx;");
	asm volatile ("rep insb;");

	asm volatile ("pop %rdi;");
	hexdump(buf, 0x40);

	printf("\n");

	/* ins port 0x43 */

	memset(buf, 0xab, sizeof(buf));

	asm volatile("push %rdi;");
	asm volatile("mov %0, %%rdi;"::"q"(buf));

	asm volatile ("mov $0x20, %rcx;");
	asm volatile ("mov $0x43, %rdx;");
	asm volatile ("rep insb;");

	asm volatile ("pop %rdi;");
	hexdump(buf, 0x40);

	printf("\n");
	return 0;
}

The vcpu->arch.pio_data buffer is used by both in/out instrutions emulation
w/o clear after using which results in some random datas are left over in
the buffer. Guest reads port 0x43 will be ignored since it is write only,
however, the function kernel_pio() can't distigush this ignore from successfully
reads data from device's ioport. There is no new data fill the buffer from
port 0x43, however, emulator_pio_in_emulated() will copy the stale data in
the buffer to the guest unconditionally. This patch fixes it by clearing the
buffer before in instruction emulation to avoid to grant guest the stale data
in the buffer.

In addition, string I/O is not supported for in kernel device. So there is no
iteration to read ioport %RCX times for string I/O. The function kernel_pio()
just reads one round, and then copy the io size * %RCX to the guest unconditionally,
actually it copies the one round ioport data w/ other random datas which are left
over in the vcpu->arch.pio_data buffer to the guest. This patch fixes it by
introducing the string I/O support for in kernel device in order to grant the right
ioport datas to the guest.

Before the patch:

0x000000: fe 38 93 93 ff ff ab ab .8......
0x000008: ab ab ab ab ab ab ab ab ........
0x000010: ab ab ab ab ab ab ab ab ........
0x000018: ab ab ab ab ab ab ab ab ........
0x000020: ab ab ab ab ab ab ab ab ........
0x000028: ab ab ab ab ab ab ab ab ........
0x000030: ab ab ab ab ab ab ab ab ........
0x000038: ab ab ab ab ab ab ab ab ........

0x000000: f6 00 00 00 00 00 00 00 ........
0x000008: 00 00 00 00 00 00 00 00 ........
0x000010: 00 00 00 00 4d 51 30 30 ....MQ00
0x000018: 30 30 20 33 20 20 20 20 00 3
0x000020: ab ab ab ab ab ab ab ab ........
0x000028: ab ab ab ab ab ab ab ab ........
0x000030: ab ab ab ab ab ab ab ab ........
0x000038: ab ab ab ab ab ab ab ab ........

0x000000: f6 00 00 00 00 00 00 00 ........
0x000008: 00 00 00 00 00 00 00 00 ........
0x000010: 00 00 00 00 4d 51 30 30 ....MQ00
0x000018: 30 30 20 33 20 20 20 20 00 3
0x000020: ab ab ab ab ab ab ab ab ........
0x000028: ab ab ab ab ab ab ab ab ........
0x000030: ab ab ab ab ab ab ab ab ........
0x000038: ab ab ab ab ab ab ab ab ........

After the patch:

0x000000: 1e 02 f8 00 ff ff ab ab ........
0x000008: ab ab ab ab ab ab ab ab ........
0x000010: ab ab ab ab ab ab ab ab ........
0x000018: ab ab ab ab ab ab ab ab ........
0x000020: ab ab ab ab ab ab ab ab ........
0x000028: ab ab ab ab ab ab ab ab ........
0x000030: ab ab ab ab ab ab ab ab ........
0x000038: ab ab ab ab ab ab ab ab ........

0x000000: d2 e2 d2 df d2 db d2 d7 ........
0x000008: d2 d3 d2 cf d2 cb d2 c7 ........
0x000010: d2 c4 d2 c0 d2 bc d2 b8 ........
0x000018: d2 b4 d2 b0 d2 ac d2 a8 ........
0x000020: ab ab ab ab ab ab ab ab ........
0x000028: ab ab ab ab ab ab ab ab ........
0x000030: ab ab ab ab ab ab ab ab ........
0x000038: ab ab ab ab ab ab ab ab ........

0x000000: 00 00 00 00 00 00 00 00 ........
0x000008: 00 00 00 00 00 00 00 00 ........
0x000010: 00 00 00 00 00 00 00 00 ........
0x000018: 00 00 00 00 00 00 00 00 ........
0x000020: ab ab ab ab ab ab ab ab ........
0x000028: ab ab ab ab ab ab ab ab ........
0x000030: ab ab ab ab ab ab ab ab ........
0x000038: ab ab ab ab ab ab ab ab ........
Reported-by: NMoguofang <moguofang@huawei.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Moguofang <moguofang@huawei.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      cbfc6c91
    • W
      KVM: x86: Fix potential preemption when get the current kvmclock timestamp · e2c2206a
      由 Wanpeng Li 提交于 
       BUG: using __this_cpu_read() in preemptible [00000000] code: qemu-system-x86/2809
 caller is __this_cpu_preempt_check+0x13/0x20
 CPU: 2 PID: 2809 Comm: qemu-system-x86 Not tainted 4.11.0+ #13
 Call Trace:
  dump_stack+0x99/0xce
  check_preemption_disabled+0xf5/0x100
  __this_cpu_preempt_check+0x13/0x20
  get_kvmclock_ns+0x6f/0x110 [kvm]
  get_time_ref_counter+0x5d/0x80 [kvm]
  kvm_hv_process_stimers+0x2a1/0x8a0 [kvm]
  ? kvm_hv_process_stimers+0x2a1/0x8a0 [kvm]
  ? kvm_arch_vcpu_ioctl_run+0xac9/0x1ce0 [kvm]
  kvm_arch_vcpu_ioctl_run+0x5bf/0x1ce0 [kvm]
  kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? __fget+0xf3/0x210
  do_vfs_ioctl+0xa4/0x700
  ? __fget+0x114/0x210
  SyS_ioctl+0x79/0x90
  entry_SYSCALL_64_fastpath+0x23/0xc2
 RIP: 0033:0x7f9d164ed357
  ? __this_cpu_preempt_check+0x13/0x20

This can be reproduced by run kvm-unit-tests/hyperv_stimer.flat w/
CONFIG_PREEMPT and CONFIG_DEBUG_PREEMPT enabled.

Safe access to per-CPU data requires a couple of constraints, though: the
thread working with the data cannot be preempted and it cannot be migrated
while it manipulates per-CPU variables. If the thread is preempted, the
thread that replaces it could try to work with the same variables; migration
to another CPU could also cause confusion. However there is no preemption
disable when reads host per-CPU tsc rate to calculate the current kvmclock
timestamp.

This patch fixes it by utilizing get_cpu/put_cpu pair to guarantee both
__this_cpu_read() and rdtsc() are not preempted.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      e2c2206a
  13. 18 5月, 2017 1 次提交
  15. 16 5月, 2017 1 次提交
  17. 15 5月, 2017 3 次提交
    • W
      KVM: VMX: Don't enable EPT A/D feature if EPT feature is disabled · fce6ac4c
      由 Wanpeng Li 提交于 
      We can observe eptad kvm_intel module parameter is still Y
even if ept is disabled which is weird. This patch will
not enable EPT A/D feature if EPT feature is disabled.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      fce6ac4c
    • W
      KVM: x86: Fix load damaged SSEx MXCSR register · a575813b
      由 Wanpeng Li 提交于 
      Reported by syzkaller:

   BUG: unable to handle kernel paging request at ffffffffc07f6a2e
   IP: report_bug+0x94/0x120
   PGD 348e12067
   P4D 348e12067
   PUD 348e14067
   PMD 3cbd84067
   PTE 80000003f7e87161

   Oops: 0003 [#1] SMP
   CPU: 2 PID: 7091 Comm: kvm_load_guest_ Tainted: G           OE   4.11.0+ #8
   task: ffff92fdfb525400 task.stack: ffffbda6c3d04000
   RIP: 0010:report_bug+0x94/0x120
   RSP: 0018:ffffbda6c3d07b20 EFLAGS: 00010202
    do_trap+0x156/0x170
    do_error_trap+0xa3/0x170
    ? kvm_load_guest_fpu.part.175+0x12a/0x170 [kvm]
    ? mark_held_locks+0x79/0xa0
    ? retint_kernel+0x10/0x10
    ? trace_hardirqs_off_thunk+0x1a/0x1c
    do_invalid_op+0x20/0x30
    invalid_op+0x1e/0x30
   RIP: 0010:kvm_load_guest_fpu.part.175+0x12a/0x170 [kvm]
    ? kvm_load_guest_fpu.part.175+0x1c/0x170 [kvm]
    kvm_arch_vcpu_ioctl_run+0xed6/0x1b70 [kvm]
    kvm_vcpu_ioctl+0x384/0x780 [kvm]
    ? kvm_vcpu_ioctl+0x384/0x780 [kvm]
    ? sched_clock+0x13/0x20
    ? __do_page_fault+0x2a0/0x550
    do_vfs_ioctl+0xa4/0x700
    ? up_read+0x1f/0x40
    ? __do_page_fault+0x2a0/0x550
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x23/0xc2

SDM mentioned that "The MXCSR has several reserved bits, and attempting to write
a 1 to any of these bits will cause a general-protection exception(#GP) to be
generated". The syzkaller forks' testcase overrides xsave area w/ random values
and steps on the reserved bits of MXCSR register. The damaged MXCSR register
values of guest will be restored to SSEx MXCSR register before vmentry. This
patch fixes it by catching userspace override MXCSR register reserved bits w/
random values and bails out immediately.
Reported-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      a575813b
    • D
      kvm: nVMX: off by one in vmx_write_pml_buffer() · 4769886b
      由 Dan Carpenter 提交于 
      There are PML_ENTITY_NUM elements in the pml_address[] array so the >
should be >= or we write beyond the end of the array when we do:

	pml_address[vmcs12->guest_pml_index--] = gpa;

Fixes: c5f983f6 ("nVMX: Implement emulated Page Modification Logging")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
      4769886b
  19. 09 5月, 2017 5 次提交
  21. 05 5月, 2017 1 次提交
  23. 03 5月, 2017 1 次提交
    • P
      Revert "KVM: Support vCPU-based gfn->hva cache" · 4e335d9e
      由 Paolo Bonzini 提交于 
      This reverts commit bbd64115.

I've been sitting on this revert for too long and it unfortunately
missed 4.11.  It's also the reason why I haven't merged ring-based
dirty tracking for 4.12.

Using kvm_vcpu_memslots in kvm_gfn_to_hva_cache_init and
kvm_vcpu_write_guest_offset_cached means that the MSR value can
now be used to access SMRAM, simply by making it point to an SMRAM
physical address.  This is problematic because it lets the guest
OS overwrite memory that it shouldn't be able to touch.

Cc: stable@vger.kernel.org
Fixes: bbd64115Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      4e335d9e
  25. 02 5月, 2017 1 次提交
  27. 27 4月, 2017 5 次提交
    • J
      kvm: nVMX: Remove superfluous VMX instruction fault checks · 70f3aac9
      由 Jim Mattson 提交于 
      According to the Intel SDM, "Certain exceptions have priority over VM
exits. These include invalid-opcode exceptions, faults based on
privilege level*, and general-protection exceptions that are based on
checking I/O permission bits in the task-state segment (TSS)."

There is no need to check for faulting conditions that the hardware
has already checked.

* These include faults generated by attempts to execute, in
  virtual-8086 mode, privileged instructions that are not recognized
  in that mode.
Signed-off-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      70f3aac9
    • L
      KVM: x86: fix emulation of RSM and IRET instructions · 6ed071f0
      由 Ladi Prosek 提交于 
      On AMD, the effect of set_nmi_mask called by emulate_iret_real and em_rsm
on hflags is reverted later on in x86_emulate_instruction where hflags are
overwritten with ctxt->emul_flags (the kvm_set_hflags call). This manifests
as a hang when rebooting Windows VMs with QEMU, OVMF, and >1 vcpu.

Instead of trying to merge ctxt->emul_flags into vcpu->arch.hflags after
an instruction is emulated, this commit deletes emul_flags altogether and
makes the emulator access vcpu->arch.hflags using two new accessors. This
way all changes, on the emulator side as well as in functions called from
the emulator and accessing vcpu state with emul_to_vcpu, are preserved.

More details on the bug and its manifestation with Windows and OVMF:

  It's a KVM bug in the interaction between SMI/SMM and NMI, specific to AMD.
  I believe that the SMM part explains why we started seeing this only with
  OVMF.

  KVM masks and unmasks NMI when entering and leaving SMM. When KVM emulates
  the RSM instruction in em_rsm, the set_nmi_mask call doesn't stick because
  later on in x86_emulate_instruction we overwrite arch.hflags with
  ctxt->emul_flags, effectively reverting the effect of the set_nmi_mask call.
  The AMD-specific hflag of interest here is HF_NMI_MASK.

  When rebooting the system, Windows sends an NMI IPI to all but the current
  cpu to shut them down. Only after all of them are parked in HLT will the
  initiating cpu finish the restart. If NMI is masked, other cpus never get
  the memo and the initiating cpu spins forever, waiting for
  hal!HalpInterruptProcessorsStarted to drop. That's the symptom we observe.

Fixes: a584539b ("KVM: x86: pass the whole hflags field to emulator and back")
Signed-off-by: NLadi Prosek <lprosek@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      6ed071f0
    • A
      KVM: add explicit barrier to kvm_vcpu_kick · cde9af6e
      由 Andrew Jones 提交于 
      kvm_vcpu_kick() must issue a general memory barrier prior to reading
vcpu->mode in order to ensure correctness of the mutual-exclusion
memory barrier pattern used with vcpu->requests.  While the cmpxchg
called from kvm_vcpu_kick():

 kvm_vcpu_kick
   kvm_arch_vcpu_should_kick
     kvm_vcpu_exiting_guest_mode
       cmpxchg

implies general memory barriers before and after the operation, that
implication is only valid when cmpxchg succeeds.  We need an explicit
barrier for when it fails, otherwise a VCPU thread on its entry path
that reads zero for vcpu->requests does not exclude the possibility
the requesting thread sees !IN_GUEST_MODE when it reads vcpu->mode.

kvm_make_all_cpus_request already had a barrier, so we remove it, as
now it would be redundant.
Signed-off-by: NAndrew Jones <drjones@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      cde9af6e
    • R
      KVM: x86: always use kvm_make_request instead of set_bit · 1bd2009e
      由 Radim Krčmář 提交于 
      Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Reviewed-by: NAndrew Jones <drjones@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      1bd2009e
    • R
      KVM: add kvm_{test,clear}_request to replace {test,clear}_bit · 72875d8a
      由 Radim Krčmář 提交于 
      Users were expected to use kvm_check_request() for testing and clearing,
but request have expanded their use since then and some users want to
only test or do a faster clear.

Make sure that requests are not directly accessed with bit operations.
Reviewed-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Reviewed-by: NAndrew Jones <drjones@redhat.com>
Reviewed-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      72875d8a
  29. 21 4月, 2017 2 次提交
    • M
      KVM: x86: remove irq disablement around KVM_SET_CLOCK/KVM_GET_CLOCK · e891a32e
      由 Marcelo Tosatti 提交于 
      The disablement of interrupts at KVM_SET_CLOCK/KVM_GET_CLOCK
attempts to disable software suspend from causing "non atomic behaviour" of
the operation:

    Add a helper function to compute the kernel time and convert nanoseconds
    back to CPU specific cycles.  Note that these must not be called in preemptible
    context, as that would mean the kernel could enter software suspend state,
    which would cause non-atomic operation.

However, assume the kernel can enter software suspend at the following 2 points:

        ktime_get_ts(&ts);
1.
						hypothetical_ktime_get_ts(&ts)
        monotonic_to_bootbased(&ts);
2.

monotonic_to_bootbased() should be correct relative to a ktime_get_ts(&ts)
performed after point 1 (that is after resuming from software suspend),
hypothetical_ktime_get_ts()

Therefore it is also correct for the ktime_get_ts(&ts) before point 1,
which is

	ktime_get_ts(&ts) = hypothetical_ktime_get_ts(&ts) + time-to-execute-suspend-code

Note CLOCK_MONOTONIC does not count during suspension.

So remove the irq disablement, which causes the following warning on
-RT kernels:

 With this reasoning, and the -RT bug that the irq disablement causes
 (because spin_lock is now a sleeping lock), remove the IRQ protection as it
 causes:

 [ 1064.668109] in_atomic(): 0, irqs_disabled(): 1, pid: 15296, name:m
 [ 1064.668110] INFO: lockdep is turned off.
 [ 1064.668110] irq event stamp: 0
 [ 1064.668112] hardirqs last  enabled at (0): [<          (null)>]  )
 [ 1064.668116] hardirqs last disabled at (0): [] c0
 [ 1064.668118] softirqs last  enabled at (0): [] c0
 [ 1064.668118] softirqs last disabled at (0): [<          (null)>]  )
 [ 1064.668121] CPU: 13 PID: 15296 Comm: qemu-kvm Not tainted 3.10.0-1
 [ 1064.668121] Hardware name: Dell Inc. PowerEdge R730/0H21J3, BIOS 5
 [ 1064.668123]  ffff8c1796b88000 00000000afe7344c ffff8c179abf3c68 f3
 [ 1064.668125]  ffff8c179abf3c90 ffffffff930ccb3d ffff8c1b992b3610 f0
 [ 1064.668126]  00007ffc1a26fbc0 ffff8c179abf3cb0 ffffffff9375f694 f0
 [ 1064.668126] Call Trace:
 [ 1064.668132]  [] dump_stack+0x19/0x1b
 [ 1064.668135]  [] __might_sleep+0x12d/0x1f0
 [ 1064.668138]  [] rt_spin_lock+0x24/0x60
 [ 1064.668155]  [] __get_kvmclock_ns+0x36/0x110 [k]
 [ 1064.668159]  [] ? futex_wait_queue_me+0x103/0x10
 [ 1064.668171]  [] kvm_arch_vm_ioctl+0xa2/0xd70 [k]
 [ 1064.668173]  [] ? futex_wait+0x1ac/0x2a0

v2: notice get_kvmclock_ns with the same problem (Pankaj).
v3: remove useless helper function (Pankaj).
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      e891a32e
    • M
      kvm: better MWAIT emulation for guests · 668fffa3
      由 Michael S. Tsirkin 提交于 
      Guests that are heavy on futexes end up IPI'ing each other a lot. That
can lead to significant slowdowns and latency increase for those guests
when running within KVM.

If only a single guest is needed on a host, we have a lot of spare host
CPU time we can throw at the problem. Modern CPUs implement a feature
called "MWAIT" which allows guests to wake up sleeping remote CPUs without
an IPI - thus without an exit - at the expense of never going out of guest
context.

The decision whether this is something sensible to use should be up to the
VM admin, so to user space. We can however allow MWAIT execution on systems
that support it properly hardware wise.

This patch adds a CAP to user space and a KVM cpuid leaf to indicate
availability of native MWAIT execution. With that enabled, the worst a
guest can do is waste as many cycles as a "jmp ." would do, so it's not
a privilege problem.

We consciously do *not* expose the feature in our CPUID bitmap, as most
people will want to benefit from sleeping vCPUs to allow for over commit.
Reported-by: N"Gabriel L. Somlo" <gsomlo@gmail.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
[agraf: fix amd, change commit message]
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
      668fffa3