[PATCH 4/4] KVM: selftests: Extend state_test to check next_rip

[Yosry Ahmed <yosry.ahmed@linux.dev>]

Similar to vGIF, extend state_test to make sure that next_rip is saved
correctly in nested state. GUEST_SYNC() in L2 causes IO emulation by
KVM, which advances the RIP to the value of next_rip. Hence, if next_rip
is saved correctly, its value should match the saved RIP value.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
---
 tools/testing/selftests/kvm/x86/state_test.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/state_test.c b/tools/testing/selftests/kvm/x86/state_test.c
index 57c7546f3d7c..992a52504a4a 100644
--- a/tools/testing/selftests/kvm/x86/state_test.c
+++ b/tools/testing/selftests/kvm/x86/state_test.c
@@ -236,6 +236,17 @@ void svm_check_nested_state(int stage, struct kvm_x86_state *state)
 		if (stage == 6)
 			TEST_ASSERT_EQ(!!(vmcb->control.int_ctl & V_GIF_MASK), 0);
 	}
+
+	if (kvm_cpu_has(X86_FEATURE_NRIPS)) {
+		/*
+		 * GUEST_SYNC() causes IO emulation in KVM, in which case the
+		 * RIP is advanced before exiting to userspace. Hence, the RIP
+		 * in the saved state should be the same as nRIP saved by the
+		 * CPU in the VMCB.
+		 */
+		if (stage == 6)
+			TEST_ASSERT_EQ(vmcb->control.next_rip, state->regs.rip);
+	}
 }
 
 void check_nested_state(int stage, struct kvm_x86_state *state)
-- 
2.53.0.rc2.204.g2597b5adb4-goog