linux-kernel - [PATCH v7 3/4] KVM: SEV-ES: Add tests to validate VC handling for MSR and DR7 register accesses

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Date:   Mon, 13 Jun 2022 19:04:19 +0200
From:   Vasant Karasulli <vkarasulli@...e.de>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     bp@...en8.de, jroedel@...e.de, thomas.lendacky@....com,
        x86@...nel.org, seanjc@...gle.com,
        Vasant Karasulli <vkarasulli@...e.de>
Subject: [PATCH v7 3/4] KVM: SEV-ES: Add tests to validate VC handling for MSR and DR7 register accesses

These tests:
   1. install a kretprobe on the #VC handler (sev_es_ghcb_hv_call, to
       access GHCB before/after the resulting VMGEXIT).
   2. trigger an NAE by accessing either MSR or DR7.
   3. check that the kretprobe was hit with the right exit_code available
      in GHCB.

To run these tests, configuration options CONFIG_X86_TESTS and
CONFIG_AMD_SEV_ES_TEST_VC have to be enabled. These tests run
at the kernel boot time. Result of the test execution can be
monitored in the kernel log.

Signed-off-by: Vasant Karasulli <vkarasulli@...e.de>
---
 arch/x86/tests/sev-test-vc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/tests/sev-test-vc.c b/arch/x86/tests/sev-test-vc.c
index 900ca357a273..629aa0ca1c86 100644
--- a/arch/x86/tests/sev-test-vc.c
+++ b/arch/x86/tests/sev-test-vc.c
@@ -7,6 +7,7 @@

 #include <asm/cpufeature.h>
 #include <asm/sev-common.h>
+#include <asm/debugreg.h>
 #include <asm/svm.h>
 #include <kunit/test.h>
 #include <linux/kprobes.h>
@@ -89,9 +90,22 @@ static void sev_es_nae_wbinvd(struct kunit *test)
 	check_op(test, SVM_EXIT_WBINVD, wbinvd());
 }

+static void sev_es_nae_msr(struct kunit *test)
+{
+	check_op(test, SVM_EXIT_MSR, __rdmsr(MSR_IA32_TSC));
+}
+
+static void sev_es_nae_dr7_rw(struct kunit *test)
+{
+	check_op(test, SVM_EXIT_WRITE_DR7,
+		   native_set_debugreg(7, native_get_debugreg(7)));
+}
+
 static struct kunit_case sev_es_vc_testcases[] = {
 	KUNIT_CASE(sev_es_nae_cpuid),
 	KUNIT_CASE(sev_es_nae_wbinvd),
+	KUNIT_CASE(sev_es_nae_msr),
+	KUNIT_CASE(sev_es_nae_dr7_rw),
 	{}
 };

--
2.32.0