1 files changed, 135 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c b/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c
new file mode 100644
index 000000000000..32f7e09ef67c
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020, Google LLC.
+ *
+ * Tests for KVM paravirtual feature disablement
+ */
+#include <asm/kvm_para.h>
+#include <linux/kvm_para.h>
+#include <linux/stringify.h>
+#include <stdint.h>
+
+#include "apic.h"
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+/* VMCALL and VMMCALL are both 3-byte opcodes. */
+#define HYPERCALL_INSN_SIZE	3
+
+static bool quirk_disabled;
+
+static void guest_ud_handler(struct ex_regs *regs)
+{
+	regs->rax = -EFAULT;
+	regs->rip += HYPERCALL_INSN_SIZE;
+}
+
+static const uint8_t vmx_vmcall[HYPERCALL_INSN_SIZE]  = { 0x0f, 0x01, 0xc1 };
+static const uint8_t svm_vmmcall[HYPERCALL_INSN_SIZE] = { 0x0f, 0x01, 0xd9 };
+
+extern uint8_t hypercall_insn[HYPERCALL_INSN_SIZE];
+static uint64_t do_sched_yield(uint8_t apic_id)
+{
+	uint64_t ret;
+
+	asm volatile("hypercall_insn:\n\t"
+		     ".byte 0xcc,0xcc,0xcc\n\t"
+		     : "=a"(ret)
+		     : "a"((uint64_t)KVM_HC_SCHED_YIELD), "b"((uint64_t)apic_id)
+		     : "memory");
+
+	return ret;
+}
+
+static void guest_main(void)
+{
+	const uint8_t *native_hypercall_insn;
+	const uint8_t *other_hypercall_insn;
+	uint64_t ret;
+
+	if (is_intel_cpu()) {
+		native_hypercall_insn = vmx_vmcall;
+		other_hypercall_insn  = svm_vmmcall;
+	} else if (is_amd_cpu()) {
+		native_hypercall_insn = svm_vmmcall;
+		other_hypercall_insn  = vmx_vmcall;
+	} else {
+		GUEST_ASSERT(0);
+		/* unreachable */
+		return;
+	}
+
+	memcpy(hypercall_insn, other_hypercall_insn, HYPERCALL_INSN_SIZE);
+
+	ret = do_sched_yield(GET_APIC_ID_FIELD(xapic_read_reg(APIC_ID)));
+
+	/*
+	 * If the quirk is disabled, verify that guest_ud_handler() "returned"
+	 * -EFAULT and that KVM did NOT patch the hypercall.  If the quirk is
+	 * enabled, verify that the hypercall succeeded and that KVM patched in
+	 * the "right" hypercall.
+	 */
+	if (quirk_disabled) {
+		GUEST_ASSERT(ret == (uint64_t)-EFAULT);
+		GUEST_ASSERT(!memcmp(other_hypercall_insn, hypercall_insn,
+			     HYPERCALL_INSN_SIZE));
+	} else {
+		GUEST_ASSERT(!ret);
+		GUEST_ASSERT(!memcmp(native_hypercall_insn, hypercall_insn,
+			     HYPERCALL_INSN_SIZE));
+	}
+
+	GUEST_DONE();
+}
+
+static void enter_guest(struct kvm_vcpu *vcpu)
+{
+	struct kvm_run *run = vcpu->run;
+	struct ucall uc;
+
+	vcpu_run(vcpu);
+	switch (get_ucall(vcpu, &uc)) {
+	case UCALL_SYNC:
+		pr_info("%s: %016lx\n", (const char *)uc.args[2], uc.args[3]);
+		break;
+	case UCALL_DONE:
+		return;
+	case UCALL_ABORT:
+		REPORT_GUEST_ASSERT(uc);
+	default:
+		TEST_FAIL("Unhandled ucall: %ld\nexit_reason: %u (%s)",
+			  uc.cmd, run->exit_reason, exit_reason_str(run->exit_reason));
+	}
+}
+
+static void test_fix_hypercall(bool disable_quirk)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_main);
+
+	vm_init_descriptor_tables(vcpu->vm);
+	vcpu_init_descriptor_tables(vcpu);
+	vm_install_exception_handler(vcpu->vm, UD_VECTOR, guest_ud_handler);
+
+	if (disable_quirk)
+		vm_enable_cap(vm, KVM_CAP_DISABLE_QUIRKS2,
+			      KVM_X86_QUIRK_FIX_HYPERCALL_INSN);
+
+	quirk_disabled = disable_quirk;
+	sync_global_to_guest(vm, quirk_disabled);
+
+	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
+
+	enter_guest(vcpu);
+}
+
+int main(void)
+{
+	TEST_REQUIRE(kvm_check_cap(KVM_CAP_DISABLE_QUIRKS2) & KVM_X86_QUIRK_FIX_HYPERCALL_INSN);
+
+	test_fix_hypercall(false);
+	test_fix_hypercall(true);
+}