[kvm-unit-tests PATCH] svm: Add SMI handler for svm_intr_intercept_mix_smi test

[Ryosuke Yasuoka <ryasuoka@redhat.com>]

L1 intercepts L2's SMI and the SMI is still pending at L0. When L1
re-enables GIF via stgi(), L0 delivers the SMI to L1. Without an SMI
handler, L1 enters SMM and aborts.

Install a trivial RSM handler at the default SMBASE entry point so L1
can return from SMM.

Signed-off-by: Ryosuke Yasuoka <ryasuoka@redhat.com>
---
 x86/svm_tests.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index ccbab1d0..11770854 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -3543,8 +3543,28 @@ static void svm_intr_intercept_mix_smi_guest(struct svm_test *test)
 	report(0, "must not reach here");
 }
 
+#define SMBASE	0x30000
+#define SMBASE_ENTRY	(SMBASE + 0x8000)
+#define RSM_OPCODE	0xaa0f
+
+/*
+ * Install a trivial SMI handler that executes RSM at the default SMBASE
+ * entry point. Without this, entering SMM causes an abort.
+ */
+static void install_smi_handler(void)
+{
+	WRITE_ONCE(*(u16 *)SMBASE_ENTRY, RSM_OPCODE);
+}
+
 static void svm_intr_intercept_mix_smi(void)
 {
+	/*
+	 * L1 intercepts L2's SMI. It makes L0 deliver the SMI to L1
+	 * when L1 re-enables GIF via stgi(), so L1 needs an SMI handler
+	 * to avoid aborting.
+	 */
+	install_smi_handler();
+
 	vmcb_set_intercept(INTERCEPT_SMI);
 	vmcb->control.int_ctl &= ~V_INTR_MASKING_MASK;
 	test_set_guest(svm_intr_intercept_mix_smi_guest);
-- 
2.55.0