KVM: selftests: Verify supported CR4 bits can be set before KVM_SET_CPUID2

Extend the KVM_SET_SREGS test to verify that all supported CR4 bits, as
enumerated by KVM, can be set before KVM_SET_CPUID2, i.e. without first
defining the vCPU model.  KVM is supposed to skip guest CPUID checks
when host userspace is stuffing guest state.

Check the inverse as well, i.e. that KVM rejects KVM_SET_REGS if CR4
has one or more unsupported bits set.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20201007014417.29276-7-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -27,6 +27,7 @@
 #define X86_CR4_OSFXSR		(1ul << 9)
 #define X86_CR4_OSXMMEXCPT	(1ul << 10)
 #define X86_CR4_UMIP		(1ul << 11)
+#define X86_CR4_LA57		(1ul << 12)
 #define X86_CR4_VMXE		(1ul << 13)
 #define X86_CR4_SMXE		(1ul << 14)
 #define X86_CR4_FSGSBASE	(1ul << 16)
@@ -36,6 +37,22 @@
 #define X86_CR4_SMAP		(1ul << 21)
 #define X86_CR4_PKE		(1ul << 22)
 
+/* CPUID.1.ECX */
+#define CPUID_VMX		(1ul << 5)
+#define CPUID_SMX		(1ul << 6)
+#define CPUID_PCID		(1ul << 17)
+#define CPUID_XSAVE		(1ul << 26)
+
+/* CPUID.7.EBX */
+#define CPUID_FSGSBASE		(1ul << 0)
+#define CPUID_SMEP		(1ul << 7)
+#define CPUID_SMAP		(1ul << 20)
+
+/* CPUID.7.ECX */
+#define CPUID_UMIP		(1ul << 2)
+#define CPUID_PKU		(1ul << 3)
+#define CPUID_LA57		(1ul << 16)
+
 #define UNEXPECTED_VECTOR_PORT 0xfff0u
 
 /* General Registers in 64-Bit Mode */

tools/testing/selftests/kvm/include/x86_64/vmx.h

@@ -11,10 +11,6 @@
 #include <stdint.h>
 #include "processor.h"
 
-#define CPUID_VMX_BIT				5
-
-#define CPUID_VMX				(1 << 5)
-
 /*
  * Definitions of Primary Processor-Based VM-Execution Controls.
  */

tools/testing/selftests/kvm/x86_64/set_sregs_test.c

@@ -24,16 +24,106 @@
 
 #define VCPU_ID                  5
 
+static void test_cr4_feature_bit(struct kvm_vm *vm, struct kvm_sregs *orig,
+				 uint64_t feature_bit)
+{
+	struct kvm_sregs sregs;
+	int rc;
+
+	/* Skip the sub-test, the feature is supported. */
+	if (orig->cr4 & feature_bit)
+		return;
+
+	memcpy(&sregs, orig, sizeof(sregs));
+	sregs.cr4 |= feature_bit;
+
+	rc = _vcpu_sregs_set(vm, VCPU_ID, &sregs);
+	TEST_ASSERT(rc, "KVM allowed unsupported CR4 bit (0x%lx)", feature_bit);
+
+	/* Sanity check that KVM didn't change anything. */
+	vcpu_sregs_get(vm, VCPU_ID, &sregs);
+	TEST_ASSERT(!memcmp(&sregs, orig, sizeof(sregs)), "KVM modified sregs");
+}
+
+static uint64_t calc_cr4_feature_bits(struct kvm_vm *vm)
+{
+	struct kvm_cpuid_entry2 *cpuid_1, *cpuid_7;
+	uint64_t cr4;
+
+	cpuid_1 = kvm_get_supported_cpuid_entry(1);
+	cpuid_7 = kvm_get_supported_cpuid_entry(7);
+
+	cr4 = X86_CR4_VME | X86_CR4_PVI | X86_CR4_TSD | X86_CR4_DE |
+	      X86_CR4_PSE | X86_CR4_PAE | X86_CR4_MCE | X86_CR4_PGE |
+	      X86_CR4_PCE | X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT;
+	if (cpuid_7->ecx & CPUID_UMIP)
+		cr4 |= X86_CR4_UMIP;
+	if (cpuid_7->ecx & CPUID_LA57)
+		cr4 |= X86_CR4_LA57;
+	if (cpuid_1->ecx & CPUID_VMX)
+		cr4 |= X86_CR4_VMXE;
+	if (cpuid_1->ecx & CPUID_SMX)
+		cr4 |= X86_CR4_SMXE;
+	if (cpuid_7->ebx & CPUID_FSGSBASE)
+		cr4 |= X86_CR4_FSGSBASE;
+	if (cpuid_1->ecx & CPUID_PCID)
+		cr4 |= X86_CR4_PCIDE;
+	if (cpuid_1->ecx & CPUID_XSAVE)
+		cr4 |= X86_CR4_OSXSAVE;
+	if (cpuid_7->ebx & CPUID_SMEP)
+		cr4 |= X86_CR4_SMEP;
+	if (cpuid_7->ebx & CPUID_SMAP)
+		cr4 |= X86_CR4_SMAP;
+	if (cpuid_7->ecx & CPUID_PKU)
+		cr4 |= X86_CR4_PKE;
+
+	return cr4;
+}
+
 int main(int argc, char *argv[])
 {
 	struct kvm_sregs sregs;
 	struct kvm_vm *vm;
+	uint64_t cr4;
 	int rc;
 
 	/* Tell stdout not to buffer its content */
 	setbuf(stdout, NULL);
 
-	/* Create VM */
+	/*
+	 * Create a dummy VM, specifically to avoid doing KVM_SET_CPUID2, and
+	 * use it to verify all supported CR4 bits can be set prior to defining
+	 * the vCPU model, i.e. without doing KVM_SET_CPUID2.
+	 */
+	vm = vm_create(VM_MODE_DEFAULT, DEFAULT_GUEST_PHY_PAGES, O_RDWR);
+	vm_vcpu_add(vm, VCPU_ID);
+
+	vcpu_sregs_get(vm, VCPU_ID, &sregs);
+
+	sregs.cr4 |= calc_cr4_feature_bits(vm);
+	cr4 = sregs.cr4;
+
+	rc = _vcpu_sregs_set(vm, VCPU_ID, &sregs);
+	TEST_ASSERT(!rc, "Failed to set supported CR4 bits (0x%lx)", cr4);
+
+	vcpu_sregs_get(vm, VCPU_ID, &sregs);
+	TEST_ASSERT(sregs.cr4 == cr4, "sregs.CR4 (0x%llx) != CR4 (0x%lx)",
+		    sregs.cr4, cr4);
+
+	/* Verify all unsupported features are rejected by KVM. */
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_UMIP);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_LA57);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_VMXE);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_SMXE);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_FSGSBASE);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_PCIDE);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_OSXSAVE);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_SMEP);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_SMAP);
+	test_cr4_feature_bit(vm, &sregs, X86_CR4_PKE);
+	kvm_vm_free(vm);
+
+	/* Create a "real" VM and verify APIC_BASE can be set. */
 	vm = vm_create_default(VCPU_ID, 0, NULL);
 
 	vcpu_sregs_get(vm, VCPU_ID, &sregs);