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Commit ca359066 authored by Wei Huang's avatar Wei Huang Committed by Paolo Bonzini
Browse files

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 c4d21882 ("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: default avatarWei Huang <wei@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent d2ce98ca

tools/testing/selftests/kvm/.gitignore

+1 −0
Original line number Diff line number Diff line 
cr4_cpuid_sync_test

set_sregs_test

sync_regs_test

vmx_tsc_adjust_test

tools/testing/selftests/kvm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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))

tools/testing/selftests/kvm/cr4_cpuid_sync_test.c

0 → 100644
+129 −0
Original line number Diff line number Diff line 
// 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;

}