[PATCH v4 18/15] selftests: kvm: add test for transferring FPU state into the VMSA

From: Paolo Bonzini
Date: Tue Mar 19 2024 - 15:44:09 EST


Test that CRn, XCR0 and FPU state are correctly moved from KVM's internal
state to the VMSA by SEV_LAUNCH_UPDATE_VMSA.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
.../selftests/kvm/x86_64/sev_smoke_test.c | 87 +++++++++++++++++++
1 file changed, 87 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c b/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c
index 234c80dd344d..195150bc5013 100644
--- a/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c
+++ b/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c
@@ -4,6 +4,7 @@
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
+#include <math.h>

#include "test_util.h"
#include "kvm_util.h"
@@ -13,6 +14,8 @@
#include "sev.h"


+#define XFEATURE_MASK_X87_AVX (XFEATURE_MASK_FP | XFEATURE_MASK_SSE | XFEATURE_MASK_YMM)
+
static void guest_sev_es_code(void)
{
/* TODO: Check CPUID after GHCB-based hypercall support is added. */
@@ -35,6 +38,84 @@ static void guest_sev_code(void)
GUEST_DONE();
}

+/* Stash state passed via VMSA before any compiled code runs. */
+extern void guest_code_xsave(void);
+asm("guest_code_xsave:\n"
+ "mov $-1, %eax\n"
+ "mov $-1, %edx\n"
+ "xsave (%rdi)\n"
+ "jmp guest_sev_es_code");
+
+static void compare_xsave(u8 *from_host, u8 *from_guest)
+{
+ int i;
+ bool bad = false;
+ for (i = 0; i < 4095; i++) {
+ if (from_host[i] != from_guest[i]) {
+ printf("mismatch at %02hhx | %02hhx %02hhx\n", i, from_host[i], from_guest[i]);
+ bad = true;
+ }
+ }
+
+ if (bad)
+ abort();
+}
+
+static void test_sync_vmsa(uint32_t policy)
+{
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ vm_vaddr_t gva;
+ void *hva;
+
+ double x87val = M_PI;
+ struct kvm_xsave __attribute__((aligned(64))) xsave = { 0 };
+ struct kvm_sregs sregs;
+ struct kvm_xcrs xcrs = {
+ .nr_xcrs = 1,
+ .xcrs[0].xcr = 0,
+ .xcrs[0].value = XFEATURE_MASK_X87_AVX,
+ };
+
+ vm = vm_sev_create_with_one_vcpu(KVM_X86_SEV_ES_VM, guest_code_xsave, &vcpu);
+ gva = vm_vaddr_alloc_shared(vm, PAGE_SIZE, KVM_UTIL_MIN_VADDR,
+ MEM_REGION_TEST_DATA);
+ hva = addr_gva2hva(vm, gva);
+
+ vcpu_args_set(vcpu, 1, gva);
+
+ vcpu_sregs_get(vcpu, &sregs);
+ sregs.cr4 |= X86_CR4_OSFXSR | X86_CR4_OSXSAVE;
+ vcpu_sregs_set(vcpu, &sregs);
+
+ vcpu_xcrs_set(vcpu, &xcrs);
+ asm("fninit; fldl %3\n"
+ "vpcmpeqb %%ymm4, %%ymm4, %%ymm4\n"
+ "xsave (%2)"
+ : "=m"(xsave)
+ : "A"(XFEATURE_MASK_X87_AVX), "r"(&xsave), "m" (x87val)
+ : "ymm4", "st", "st(1)", "st(2)", "st(3)", "st(4)", "st(5)", "st(6)", "st(7)");
+ vcpu_xsave_set(vcpu, &xsave);
+
+ vm_sev_launch(vm, SEV_POLICY_ES | policy, NULL);
+
+ /* This page is shared, so make it decrypted. */
+ memset(hva, 0, 4096);
+
+ vcpu_run(vcpu);
+
+ TEST_ASSERT(vcpu->run->exit_reason == KVM_EXIT_SYSTEM_EVENT,
+ "Wanted SYSTEM_EVENT, got %s",
+ exit_reason_str(vcpu->run->exit_reason));
+ TEST_ASSERT_EQ(vcpu->run->system_event.type, KVM_SYSTEM_EVENT_SEV_TERM);
+ TEST_ASSERT_EQ(vcpu->run->system_event.ndata, 1);
+ TEST_ASSERT_EQ(vcpu->run->system_event.data[0], GHCB_MSR_TERM_REQ);
+
+ compare_xsave((u8 *)&xsave, (u8 *)hva);
+
+ kvm_vm_free(vm);
+}
+
static void test_sev(void *guest_code, uint64_t policy)
{
struct kvm_vcpu *vcpu;
@@ -87,6 +168,12 @@ int main(int argc, char *argv[])
if (kvm_cpu_has(X86_FEATURE_SEV_ES)) {
test_sev(guest_sev_es_code, SEV_POLICY_ES | SEV_POLICY_NO_DBG);
test_sev(guest_sev_es_code, SEV_POLICY_ES);
+
+ if (kvm_has_cap(KVM_CAP_XCRS) &&
+ (xgetbv(0) & XFEATURE_MASK_X87_AVX) == XFEATURE_MASK_X87_AVX) {
+ test_sync_vmsa(0);
+ test_sync_vmsa(SEV_POLICY_NO_DBG);
+ }
}

return 0;
--
2.43.0