Commit 0326cc6b authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: selftests: Query module param to detect FEP in MSR filtering test 



Add a helper to detect KVM support for forced emulation by querying the
module param, and use the helper to detect support for the MSR filtering
test instead of throwing a noodle/NOP at KVM to see if it sticks.

Cc: Aaron Lewis <aaronlewis@google.com>
Tested-by: default avatarDapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-25-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 45e4755c

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

+5 −0
Original line number Diff line number Diff line
@@ -1222,6 +1222,11 @@ static inline bool kvm_is_pmu_enabled(void) 
	return get_kvm_param_bool("enable_pmu");

}



static inline bool kvm_is_forced_emulation_enabled(void)

{

	return !!get_kvm_param_integer("force_emulation_prefix");

}



uint64_t *__vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr,

				    int *level);

uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr);

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

+9 −18
Original line number Diff line number Diff line
@@ -14,8 +14,7 @@ 


/* Forced emulation prefix, used to invoke the emulator unconditionally. */

#define KVM_FEP "ud2; .byte 'k', 'v', 'm';"

#define KVM_FEP_LENGTH 5

static int fep_available = 1;

static bool fep_available;



#define MSR_NON_EXISTENT 0x474f4f00
@@ -260,13 +259,6 @@ static void guest_code_filter_allow(void) 
	GUEST_ASSERT(data == 2);

	GUEST_ASSERT(guest_exception_count == 0);



	/*

	 * Test to see if the instruction emulator is available (ie: the module

	 * parameter 'kvm.force_emulation_prefix=1' is set).  This instruction

	 * will #UD if it isn't available.

	 */

	__asm__ __volatile__(KVM_FEP "nop");



	if (fep_available) {

		/* Let userspace know we aren't done. */

		GUEST_SYNC(0);
@@ -388,12 +380,6 @@ static void guest_fep_gp_handler(struct ex_regs *regs) 
			   &em_wrmsr_start, &em_wrmsr_end);

}



static void guest_ud_handler(struct ex_regs *regs)

{

	fep_available = 0;

	regs->rip += KVM_FEP_LENGTH;

}



static void check_for_guest_assert(struct kvm_vcpu *vcpu)

{

	struct ucall uc;
@@ -531,9 +517,11 @@ static void test_msr_filter_allow(void) 
{

	struct kvm_vcpu *vcpu;

	struct kvm_vm *vm;

	uint64_t cmd;

	int rc;



	vm = vm_create_with_one_vcpu(&vcpu, guest_code_filter_allow);

	sync_global_to_guest(vm, fep_available);



	rc = kvm_check_cap(KVM_CAP_X86_USER_SPACE_MSR);

	TEST_ASSERT(rc, "KVM_CAP_X86_USER_SPACE_MSR is available");
@@ -561,11 +549,11 @@ static void test_msr_filter_allow(void) 
	run_guest_then_process_wrmsr(vcpu, MSR_NON_EXISTENT);

	run_guest_then_process_rdmsr(vcpu, MSR_NON_EXISTENT);



	vm_install_exception_handler(vm, UD_VECTOR, guest_ud_handler);

	vcpu_run(vcpu);

	vm_install_exception_handler(vm, UD_VECTOR, NULL);

	cmd = process_ucall(vcpu);



	if (process_ucall(vcpu) != UCALL_DONE) {

	if (fep_available) {

		TEST_ASSERT_EQ(cmd, UCALL_SYNC);

		vm_install_exception_handler(vm, GP_VECTOR, guest_fep_gp_handler);



		/* Process emulated rdmsr and wrmsr instructions. */
@@ -583,6 +571,7 @@ static void test_msr_filter_allow(void) 
		/* Confirm the guest completed without issues. */

		run_guest_then_process_ucall_done(vcpu);

	} else {

		TEST_ASSERT_EQ(cmd, UCALL_DONE);

		printf("To run the instruction emulated tests set the module parameter 'kvm.force_emulation_prefix=1'\n");

	}
@@ -804,6 +793,8 @@ static void test_user_exit_msr_flags(void) 


int main(int argc, char *argv[])

{

	fep_available = kvm_is_forced_emulation_enabled();



	test_msr_filter_allow();



	test_msr_filter_deny();