[PATCH v2 6/6] KVM: selftests: Add XCR0 Test

[Aaron Lewis <aaronlewis@google.com>]

Test that the supported xfeatures, i.e. EDX:EAX of CPUID.(EAX=0DH,ECX=0),
don't set userspace up for failure.

Though it isn't architectural, test that the supported xfeatures
aren't set in a half baked state that will cause a #GP if used to
execute XSETBV.

Check that the rules for XCR0 described in the SDM vol 1, section
13.3 ENABLING THE XSAVE FEATURE SET AND XSAVE-ENABLED FEATURES, are
followed for the supported xfeatures too.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../selftests/kvm/x86_64/xcr0_cpuid_test.c    | 121 ++++++++++++++++++
 2 files changed, 122 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/x86_64/xcr0_cpuid_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 1750f91dd9362..e2e56c82b8a90 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -104,6 +104,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_tsc_adjust_test
 TEST_GEN_PROGS_x86_64 += x86_64/vmx_nested_tsc_scaling_test
 TEST_GEN_PROGS_x86_64 += x86_64/xapic_ipi_test
 TEST_GEN_PROGS_x86_64 += x86_64/xapic_state_test
+TEST_GEN_PROGS_x86_64 += x86_64/xcr0_cpuid_test
 TEST_GEN_PROGS_x86_64 += x86_64/xss_msr_test
 TEST_GEN_PROGS_x86_64 += x86_64/debug_regs
 TEST_GEN_PROGS_x86_64 += x86_64/tsc_msrs_test
diff --git a/tools/testing/selftests/kvm/x86_64/xcr0_cpuid_test.c b/tools/testing/selftests/kvm/x86_64/xcr0_cpuid_test.c
new file mode 100644
index 0000000000000..6bef362872154
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/xcr0_cpuid_test.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * XCR0 cpuid test
+ *
+ * Copyright (C) 2022, Google LLC.
+ */
+
+#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 "processor.h"
+
+static uint64_t get_supported_user_xfeatures(void)
+{
+	uint32_t a, b, c, d;
+
+	cpuid(0xd, &a, &b, &c, &d);
+
+	return a | ((uint64_t)d << 32);
+}
+
+static void guest_code(void)
+{
+	uint64_t xcr0_rest;
+	uint64_t supported_xcr0;
+	uint64_t xfeature_mask;
+	uint64_t supported_state;
+
+	set_cr4(get_cr4() | X86_CR4_OSXSAVE);
+
+	xcr0_rest = xgetbv(0);
+	supported_xcr0 = get_supported_user_xfeatures();
+
+	GUEST_ASSERT(xcr0_rest == 1ul);
+
+	/* Check AVX */
+	xfeature_mask = XFEATURE_MASK_SSE | XFEATURE_MASK_YMM;
+	supported_state = supported_xcr0 & xfeature_mask;
+	GUEST_ASSERT(supported_state != XFEATURE_MASK_YMM);
+
+	/* Check MPX */
+	xfeature_mask = XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR;
+	supported_state = supported_xcr0 & xfeature_mask;
+	GUEST_ASSERT((supported_state == xfeature_mask) ||
+		     (supported_state == 0ul));
+
+	/* Check AVX-512 */
+	xfeature_mask = XFEATURE_MASK_SSE | XFEATURE_MASK_YMM |
+			XFEATURE_MASK_AVX512;
+	supported_state = supported_xcr0 & xfeature_mask;
+	GUEST_ASSERT((supported_state == xfeature_mask) ||
+		     ((supported_state & XFEATURE_MASK_AVX512) == 0ul));
+
+	/* Check AMX */
+	xfeature_mask = XFEATURE_MASK_XTILE;
+	supported_state = supported_xcr0 & xfeature_mask;
+	GUEST_ASSERT((supported_state == xfeature_mask) ||
+		     (supported_state == 0ul));
+
+	GUEST_SYNC(0);
+
+	xsetbv(0, supported_xcr0);
+
+	GUEST_DONE();
+}
+
+static void guest_gp_handler(struct ex_regs *regs)
+{
+	GUEST_ASSERT(!"Failed to set the supported xfeature bits in XCR0.");
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_run *run;
+	struct kvm_vm *vm;
+	struct ucall uc;
+
+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XSAVE));
+
+	/* Tell stdout not to buffer its content */
+	setbuf(stdout, NULL);
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+	run = vcpu->run;
+
+	vm_init_descriptor_tables(vm);
+	vcpu_init_descriptor_tables(vcpu);
+
+	while (1) {
+		vcpu_run(vcpu);
+
+		TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+			    "Unexpected exit reason: %u (%s),\n",
+			    run->exit_reason,
+			    exit_reason_str(run->exit_reason));
+
+		switch (get_ucall(vcpu, &uc)) {
+		case UCALL_SYNC:
+			vm_install_exception_handler(vm, GP_VECTOR,
+						     guest_gp_handler);
+			break;
+		case UCALL_ABORT:
+			REPORT_GUEST_ASSERT(uc);
+			break;
+		case UCALL_DONE:
+			goto done;
+		default:
+			TEST_FAIL("Unknown ucall %lu", uc.cmd);
+		}
+	}
+
+done:
+	kvm_vm_free(vm);
+	return 0;
+}
-- 
2.39.0.314.g84b9a713c41-goog