From 0de704d2d6c82c7498fa1b8df66903f8139e3de2 Mon Sep 17 00:00:00 2001 From: Michal Luczaj Date: Fri, 28 Jul 2023 02:12:58 +0200 Subject: [PATCH] KVM: selftests: Extend x86's sync_regs_test to check for exception races 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 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 --- .../testing/selftests/kvm/x86_64/sync_regs_test.c | 23 ++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c index e4ff2eaad7cd..7e5b13869e2e 100644 --- a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c +++ b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c @@ -82,6 +82,28 @@ static void compare_vcpu_events(struct kvm_vcpu_events *left, #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; } -- 2.11.0