Commit b774da3f authored by Ben Gardon's avatar Ben Gardon Committed by Paolo Bonzini
Browse files

KVM: selftests: Test disabling NX hugepages on a VM 



Add an argument to the NX huge pages test to test disabling the feature
on a VM using the new capability.

Reviewed-by: default avatarDavid Matlack <dmatlack@google.com>
Signed-off-by: default avatarBen Gardon <bgardon@google.com>
Message-Id: <20220613212523.3436117-10-bgardon@google.com>
[Handle failure of sudo or setcap more gracefully. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 8448ec59

tools/testing/selftests/kvm/include/kvm_util_base.h

+6 −0
Original line number Diff line number Diff line
@@ -809,4 +809,10 @@ static inline void virt_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent) 
	virt_arch_dump(stream, vm, indent);

}





static inline int __vm_disable_nx_huge_pages(struct kvm_vm *vm)

{

	return __vm_enable_cap(vm, KVM_CAP_VM_DISABLE_NX_HUGE_PAGES, 0);

}



#endif /* SELFTEST_KVM_UTIL_BASE_H */

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

+87 −47
Original line number Diff line number Diff line
@@ -107,53 +107,34 @@ static void wait_for_reclaim(int reclaim_period_ms) 
	nanosleep(&ts, NULL);

}



static void help(char *name)

{

	puts("");

	printf("usage: %s [-h] [-p period_ms] [-t token]\n", name);

	puts("");

	printf(" -p: The NX reclaim period in miliseconds.\n");

	printf(" -t: The magic token to indicate environment setup is done.\n");

	puts("");

	exit(0);

}



int main(int argc, char **argv)

void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,

	      bool reboot_permissions)

{

	int reclaim_period_ms = 0, token = 0, opt;

	struct kvm_vcpu *vcpu;

	struct kvm_vm *vm;

	void *hva;

	int r;



	while ((opt = getopt(argc, argv, "hp:t:")) != -1) {

		switch (opt) {

		case 'p':

			reclaim_period_ms = atoi(optarg);

			break;

		case 't':

			token = atoi(optarg);

			break;

		case 'h':

		default:

			help(argv[0]);

			break;

		}

	}

	vm = vm_create(1);



	if (token != MAGIC_TOKEN) {

		print_skip("This test must be run with the magic token %d.\n"

			   "This is done by nx_huge_pages_test.sh, which\n"

			   "also handles environment setup for the test.",

			   MAGIC_TOKEN);

		exit(KSFT_SKIP);

	if (disable_nx_huge_pages) {

		/*

		 * Cannot run the test without NX huge pages if the kernel

		 * does not support it.

		 */

		if (!kvm_check_cap(KVM_CAP_VM_DISABLE_NX_HUGE_PAGES))

			return;



		r = __vm_disable_nx_huge_pages(vm);

		if (reboot_permissions) {

			TEST_ASSERT(!r, "Disabling NX huge pages should succeed if process has reboot permissions");

		} else {

			TEST_ASSERT(r == -1 && errno == EPERM,

				    "This process should not have permission to disable NX huge pages");

			return;

		}



	if (!reclaim_period_ms) {

		print_skip("The NX reclaim period must be specified and non-zero");

		exit(KSFT_SKIP);

	}



	vm = vm_create(1);

	vcpu = vm_vcpu_add(vm, 0, guest_code);



	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS_HUGETLB,
@@ -187,31 +168,38 @@ int main(int argc, char **argv) 
	/*

	 * Next, the guest will execute from the first huge page, causing it

	 * to be remapped at 4k.

	 *

	 * If NX huge pages are disabled, this should have no effect.

	 */

	vcpu_run(vcpu);

	check_2m_page_count(vm, 1);

	check_split_count(vm, 1);

	check_2m_page_count(vm, disable_nx_huge_pages ? 2 : 1);

	check_split_count(vm, disable_nx_huge_pages ? 0 : 1);



	/*

	 * Executing from the third huge page (previously unaccessed) will

	 * cause part to be mapped at 4k.

	 *

	 * If NX huge pages are disabled, it should be mapped at 2M.

	 */

	vcpu_run(vcpu);

	check_2m_page_count(vm, 1);

	check_split_count(vm, 2);

	check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);

	check_split_count(vm, disable_nx_huge_pages ? 0 : 2);



	/* Reading from the first huge page again should have no effect. */

	vcpu_run(vcpu);

	check_2m_page_count(vm, 1);

	check_split_count(vm, 2);

	check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);

	check_split_count(vm, disable_nx_huge_pages ? 0 : 2);



	/* Give recovery thread time to run. */

	wait_for_reclaim(reclaim_period_ms);



	/*

	 * Now that the reclaimer has run, all the split pages should be gone.

	 *

	 * If NX huge pages are disabled, the relaimer will not run, so

	 * nothing should change from here on.

	 */

	check_2m_page_count(vm, 1);

	check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 1);

	check_split_count(vm, 0);



	/*
@@ -219,10 +207,62 @@ int main(int argc, char **argv) 
	 * reading from it causes a huge page mapping to be installed.

	 */

	vcpu_run(vcpu);

	check_2m_page_count(vm, 2);

	check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 2);

	check_split_count(vm, 0);



	kvm_vm_free(vm);

}



static void help(char *name)

{

	puts("");

	printf("usage: %s [-h] [-p period_ms] [-t token]\n", name);

	puts("");

	printf(" -p: The NX reclaim period in miliseconds.\n");

	printf(" -t: The magic token to indicate environment setup is done.\n");

	printf(" -r: The test has reboot permissions and can disable NX huge pages.\n");

	puts("");

	exit(0);

}



int main(int argc, char **argv)

{

	int reclaim_period_ms = 0, token = 0, opt;

	bool reboot_permissions = false;



	while ((opt = getopt(argc, argv, "hp:t:r")) != -1) {

		switch (opt) {

		case 'p':

			reclaim_period_ms = atoi(optarg);

			break;

		case 't':

			token = atoi(optarg);

			break;

		case 'r':

			reboot_permissions = true;

			break;

		case 'h':

		default:

			help(argv[0]);

			break;

		}

	}



	if (token != MAGIC_TOKEN) {

		print_skip("This test must be run with the magic token %d.\n"

			   "This is done by nx_huge_pages_test.sh, which\n"

			   "also handles environment setup for the test.",

			   MAGIC_TOKEN);

		exit(KSFT_SKIP);

	}



	if (!reclaim_period_ms) {

		print_skip("The NX reclaim period must be specified and non-zero");

		exit(KSFT_SKIP);

	}



	run_test(reclaim_period_ms, false, reboot_permissions);

	run_test(reclaim_period_ms, true, reboot_permissions);



	return 0;

}

tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh

+20 −1
Original line number Diff line number Diff line
@@ -20,6 +20,10 @@ function sudo_echo () { 
	echo "$1" | sudo tee -a "$2" > /dev/null

}



NXECUTABLE="$(dirname $0)/nx_huge_pages_test"



sudo_echo test /dev/null || exit 4 # KSFT_SKIP=4



(

	set -e
@@ -28,7 +32,22 @@ function sudo_echo () { 
	sudo_echo 100 /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms

	sudo_echo "$(( $HUGE_PAGES + 3 ))" /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages



	"$(dirname $0)"/nx_huge_pages_test -t 887563923 -p 100

	# Test with reboot permissions

	if [ $(whoami) == "root" ] || sudo setcap cap_sys_boot+ep $NXECUTABLE 2> /dev/null; then

		echo Running test with CAP_SYS_BOOT enabled

		$NXECUTABLE -t 887563923 -p 100 -r

		test $(whoami) == "root" || sudo setcap cap_sys_boot-ep $NXECUTABLE

	else

		echo setcap failed, skipping nx_huge_pages_test with CAP_SYS_BOOT enabled

	fi



	# Test without reboot permissions

	if [ $(whoami) != "root" ] ; then

		echo Running test with CAP_SYS_BOOT disabled

		$NXECUTABLE -t 887563923 -p 100

	else

		echo Running as root, skipping nx_huge_pages_test with CAP_SYS_BOOT disabled

	fi

)

RET=$?