[PATCH 2/2] KVM: selftests: Verify the events half of the sync regs region

[Hemanth Selam <hemanth.selam@gmail.com>]

set_and_verify_various() writes to the regs and sregs halves of the
kvm_run sync region and checks that KVM picks them up, but it has never
done the same for events, hence the TODO.

Mask NMIs through the sync region and verify KVM applies it.  Masking is
a state change rather than an injected event, and the guest is a tight
loop that never executes IRET, so nothing can unmask NMIs behind the
test's back and the check does not depend on timing.

Assisted-by: Cursor:claude-opus-5
Signed-off-by: Hemanth Selam <hemanth.selam@gmail.com>
---
 tools/testing/selftests/kvm/x86/sync_regs_test.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86/sync_regs_test.c b/tools/testing/selftests/kvm/x86/sync_regs_test.c
index c7d1f3cca16e..b417eb0ab0f0 100644
--- a/tools/testing/selftests/kvm/x86/sync_regs_test.c
+++ b/tools/testing/selftests/kvm/x86/sync_regs_test.c
@@ -372,10 +372,15 @@ KVM_ONE_VCPU_TEST(sync_regs_test, set_and_verify_various, guest_code)
 	/* Set and verify various register values. */
 	run->s.regs.regs.rbx = 0xBAD1DEA;
 	run->s.regs.sregs.apic_base = 1 << 11;
-	/* TODO run->s.regs.events.XYZ = ABC; */
+	/*
+	 * The guest never executes IRET, so masking NMIs is a state change
+	 * KVM has to hand back unchanged, without needing an event injected.
+	 */
+	run->s.regs.events.nmi.masked = 1;
+	run->s.regs.events.flags = 0;
 
 	run->kvm_valid_regs = TEST_SYNC_FIELDS;
-	run->kvm_dirty_regs = KVM_SYNC_X86_REGS | KVM_SYNC_X86_SREGS;
+	run->kvm_dirty_regs = TEST_SYNC_FIELDS;
 	vcpu_run(vcpu);
 	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
 	TEST_ASSERT(run->s.regs.regs.rbx == 0xBAD1DEA + 1,
@@ -384,6 +389,8 @@ KVM_ONE_VCPU_TEST(sync_regs_test, set_and_verify_various, guest_code)
 	TEST_ASSERT(run->s.regs.sregs.apic_base == 1 << 11,
 		    "apic_base sync regs value incorrect 0x%llx.",
 		    run->s.regs.sregs.apic_base);
+	TEST_ASSERT(run->s.regs.events.nmi.masked,
+		    "events sync regs value incorrect, NMIs not masked");
 
 	vcpu_regs_get(vcpu, &regs);
 	compare_regs(&regs, &run->s.regs.regs);
-- 
2.43.7