kvm: selftests: add cr4_cpuid_sync_test

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@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 63fc1ab9248faee709e2a735c173a36747192cfe..8fb7903f6643c6805d70cef7d49e5a62d51fbcc2 100644 (file)
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -1,3 +1,4 @@
+cr4_cpuid_sync_test
 set_sregs_test
 sync_regs_test
 vmx_tsc_adjust_test

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index d9d00319b07cd691848a2f468c48e3bf10127284..65bda4fb0ad6da1d5bcc374e637afec1434f7340 100644 (file)
--- 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 (file)
index 0000000..8346b33
--- /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@redhat.com>
+ */
+
+#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(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;
+}