KVM is supposed to update some guest VM's CPUID bits (e.g. OSXSAVE) when
CR4 is changed. A bug was found in KVM recently and it was fixed by
Commit c4d2188206ba ("KVM: x86: Update cpuid properly when CR4.OSXAVE or
CR4.PKE is changed"). This patch adds a test to verify the synchronization
between guest VM's CR4 and CPUID bits.
Signed-off-by: Wei Huang <wei@xxxxxxxxxx>
---
tools/testing/selftests/kvm/Makefile | 1 +
tools/testing/selftests/kvm/cr4_cpuid_sync_test.c | 129 ++++++++++++++++++++++
2 files changed, 130 insertions(+)
create mode 100644 tools/testing/selftests/kvm/cr4_cpuid_sync_test.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index d9d0031..65bda4f 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -9,6 +9,7 @@ LIBKVM_x86_64 = lib/x86.c lib/vmx.c
TEST_GEN_PROGS_x86_64 = set_sregs_test
TEST_GEN_PROGS_x86_64 += sync_regs_test
TEST_GEN_PROGS_x86_64 += vmx_tsc_adjust_test
+TEST_GEN_PROGS_x86_64 += cr4_cpuid_sync_test
TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M))
LIBKVM += $(LIBKVM_$(UNAME_M))
diff --git a/tools/testing/selftests/kvm/cr4_cpuid_sync_test.c b/tools/testing/selftests/kvm/cr4_cpuid_sync_test.c
new file mode 100644
index 0000000..dbbaf3c
--- /dev/null
+++ b/tools/testing/selftests/kvm/cr4_cpuid_sync_test.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CR4 and CPUID sync test
+ *
+ * Copyright 2018, Red Hat, Inc. and/or its affiliates.
+ *
+ * Author:
+ * Wei Huang <wei@xxxxxxxxxx>
+ */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+
+#include "kvm_util.h"
+#include "x86.h"
+
+#define X86_FEATURE_XSAVE (1<<26)
+#define X86_FEATURE_OSXSAVE (1<<27)
+#define VCPU_ID 1
+
+enum {
+ GUEST_UPDATE_CR4 = 0x1000,
+ GUEST_FAILED,
+ GUEST_DONE,
+};
+
+static void exit_to_hv(uint16_t port)
+{
+ __asm__ __volatile__("in %[port], %%al"
+ :
+ : [port]"d"(port)
+ : "rax");
+}
+
+static inline bool cr4_cpuid_is_sync(void)
+{
+ int func, subfunc;
+ uint32_t eax, ebx, ecx, edx;
+ uint64_t cr4;
+
+ func = 0x1;
+ subfunc = 0x0;
+ __asm__ __volatile__("cpuid"
+ : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
+ : "a"(func), "c"(subfunc));
+
+ cr4 = get_cr4();
+
+ return (!!(ecx & X86_FEATURE_OSXSAVE)) == (!!(cr4 & X86_CR4_OSXSAVE));
+}
+
+static void guest_code(void)
+{
+ uint64_t cr4;
+
+ /* turn on CR4.OSXSAVE */
+ cr4 = get_cr4();
+ cr4 |= X86_CR4_OSXSAVE;
+ set_cr4(cr4);
+
+ /* verify CR4.OSXSAVE == CPUID.OSXSAVE */
+ if (!cr4_cpuid_is_sync())
+ exit_to_hv(GUEST_FAILED);
+
+ /* notify hypervisor to change CR4 */
+ exit_to_hv(GUEST_UPDATE_CR4);
+
+ /* check again */
+ if (!cr4_cpuid_is_sync())
+ exit_to_hv(GUEST_FAILED);
+
+ exit_to_hv(GUEST_DONE);
+}
+
+int main(int argc, char *argv[])
+{
+ struct kvm_run *run;
+ struct kvm_vm *vm;
+ struct kvm_sregs sregs;
+ struct kvm_cpuid_entry2 *entry;
+ int rc;
+
+ entry = kvm_get_supported_cpuid_entry(1);
+ if (!(entry->ecx & X86_FEATURE_XSAVE)) {
+ printf("XSAVE feature not supported, skipping test\n");
+ return 0;
+ }
+
+ /* Tell stdout not to buffer its content */
+ setbuf(stdout, NULL);
+
+ /* Create VM */
+ vm = vm_create_default_vmx(VCPU_ID, guest_code);
+ vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
+ run = vcpu_state(vm, VCPU_ID);
+
+ while (1) {
+ rc = _vcpu_run(vm, VCPU_ID);
+
+ if (run->exit_reason == KVM_EXIT_IO) {
+ switch (run->io.port) {
+ case GUEST_UPDATE_CR4:
+ /* emulate hypervisor clearing CR4.OSXSAVE */
+ vcpu_sregs_get(vm, VCPU_ID, &sregs);
+ sregs.cr4 &= ~X86_CR4_OSXSAVE;
+ vcpu_sregs_set(vm, VCPU_ID, &sregs);
+ break;
+ case GUEST_FAILED:
+ TEST_ASSERT(false, "Guest CR4 bit (OSXSAVE) unsynchronized with CPUID bit.");
+ break;
+ case GUEST_DONE:
+ goto done;
+ default:
+ TEST_ASSERT(false, "Unknown port 0x%x.",
+ run->io.port);
+ }
+ }
+ }
+
+ kvm_vm_free(vm);
+
+done:
+ return 0;
+}
--
1.8.3.1
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