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 <[email protected]>
---
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 <[email protected]>
+ */
+
+#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
On 26/06/2018 05:41, Wei Huang wrote:
> 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 <[email protected]>
> ---
> 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 <[email protected]>
> + */
> +
> +#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;
> +}
>
Queued, thanks.
Paolo