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KVM: selftests: Extend x86's sync_regs_test to check for exception races

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Attempt to set the to-be-queued exception to be both pending and injected
_after_ KVM_CAP_SYNC_REGS's kvm_vcpu_ioctl_x86_set_vcpu_events() squashes
the pending exception (if there's also an injected exception).  Buggy KVM
versions will eventually yell loudly about having impossible state when
processing queued excpetions, e.g.

  WARNING: CPU: 0 PID: 1115 at arch/x86/kvm/x86.c:10095 kvm_check_and_inject_events+0x220/0x500 [kvm]

  arch/x86/kvm/x86.c:kvm_check_and_inject_events():
  WARN_ON_ONCE(vcpu->arch.exception.injected &&
	       vcpu->arch.exception.pending);

Signed-off-by: Michal Luczaj <mhal@rbox.co>
Link: https://lore.kernel.org/r/20230728001606.2275586-3-mhal@rbox.co
[sean: split to separate patch, massage changelog and comment]
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Michal Luczaj
2023-07-28 02:12:58 +02:00
committed by Sean Christopherson
parent 60c4063b47
commit 0de704d2d6
1 changed files with 23 additions and 0 deletions
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23
tools/testing/selftests/kvm/x86_64/sync_regs_test.c
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@@ -81,6 +81,28 @@ static void compare_vcpu_events(struct kvm_vcpu_events *left,
#define TEST_SYNC_FIELDS (KVM_SYNC_X86_REGS|KVM_SYNC_X86_SREGS|KVM_SYNC_X86_EVENTS)
#define INVALID_SYNC_FIELD 0x80000000
/*
* Set an exception as pending *and* injected while KVM is processing events.
* KVM is supposed to ignore/drop pending exceptions if userspace is also
* requesting that an exception be injected.
*/
static void *race_events_inj_pen(void *arg)
{
struct kvm_run *run = (struct kvm_run *)arg;
struct kvm_vcpu_events *events = &run->s.regs.events;
for (;;) {
WRITE_ONCE(run->kvm_dirty_regs, KVM_SYNC_X86_EVENTS);
WRITE_ONCE(events->flags, 0);
WRITE_ONCE(events->exception.injected, 1);
WRITE_ONCE(events->exception.pending, 1);
pthread_testcancel();
}
return NULL;
}
/*
* Set an invalid exception vector while KVM is processing events. KVM is
* supposed to reject any vector >= 32, as well as NMIs (vector 2).
@@ -311,6 +333,7 @@ int main(int argc, char *argv[])
race_sync_regs(race_sregs_cr4);
race_sync_regs(race_events_exc);
race_sync_regs(race_events_inj_pen);
return 0;
}