Commit 0119cb36 authored by Ben Gardon's avatar Ben Gardon Committed by Paolo Bonzini
Browse files

KVM: selftests: Add configurable demand paging delay 



When running the demand paging test with the -u option, the User Fault
FD handler essentially adds an arbitrary delay to page fault resolution.
To enable better simulation of a real demand paging scenario, add a
configurable delay to the UFFD handler.

Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarBen Gardon <bgardon@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4f72180e

tools/testing/selftests/kvm/demand_paging_test.c

+25 −7
Original line number Diff line number Diff line
@@ -145,6 +145,7 @@ bool quit_uffd_thread; 
struct uffd_handler_args {

	int uffd;

	int pipefd;

	useconds_t delay;

};



static void *uffd_handler_thread_fn(void *arg)
@@ -152,6 +153,7 @@ static void *uffd_handler_thread_fn(void *arg) 
	struct uffd_handler_args *uffd_args = (struct uffd_handler_args *)arg;

	int uffd = uffd_args->uffd;

	int pipefd = uffd_args->pipefd;

	useconds_t delay = uffd_args->delay;

	int64_t pages = 0;



	while (!quit_uffd_thread) {
@@ -212,6 +214,8 @@ static void *uffd_handler_thread_fn(void *arg) 
		if (!(msg.event & UFFD_EVENT_PAGEFAULT))

			continue;



		if (delay)

			usleep(delay);

		addr =  msg.arg.pagefault.address;

		r = handle_uffd_page_request(uffd, addr);

		if (r < 0)
@@ -223,7 +227,8 @@ static void *uffd_handler_thread_fn(void *arg) 
}



static int setup_demand_paging(struct kvm_vm *vm,

			       pthread_t *uffd_handler_thread, int pipefd)

			       pthread_t *uffd_handler_thread, int pipefd,

			       useconds_t uffd_delay)

{

	int uffd;

	struct uffdio_api uffdio_api;
@@ -264,6 +269,7 @@ static int setup_demand_paging(struct kvm_vm *vm, 


	uffd_args.uffd = uffd;

	uffd_args.pipefd = pipefd;

	uffd_args.delay = uffd_delay;

	pthread_create(uffd_handler_thread, NULL, uffd_handler_thread_fn,

		       &uffd_args);
@@ -273,7 +279,8 @@ static int setup_demand_paging(struct kvm_vm *vm, 
#define GUEST_MEM_SHIFT 30 /* 1G */

#define PAGE_SHIFT_4K  12



static void run_test(enum vm_guest_mode mode, bool use_uffd)

static void run_test(enum vm_guest_mode mode, bool use_uffd,

		     useconds_t uffd_delay)

{

	pthread_t vcpu_thread;

	pthread_t uffd_handler_thread;
@@ -341,7 +348,8 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd) 
		r = pipe2(pipefd, O_CLOEXEC | O_NONBLOCK);

		TEST_ASSERT(!r, "Failed to set up pipefd");



		r = setup_demand_paging(vm, &uffd_handler_thread, pipefd[0]);

		r = setup_demand_paging(vm, &uffd_handler_thread, pipefd[0],

					uffd_delay);

		if (r < 0)

			exit(-r);

	}
@@ -395,7 +403,7 @@ static void help(char *name) 
	int i;



	puts("");

	printf("usage: %s [-h] [-m mode] [-u]\n", name);

	printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n", name);

	printf(" -m: specify the guest mode ID to test\n"

	       "     (default: test all supported modes)\n"

	       "     This option may be used multiple times.\n"
@@ -404,7 +412,11 @@ static void help(char *name) 
		printf("         %d:    %s%s\n", i, vm_guest_mode_string(i),

		       guest_modes[i].supported ? " (supported)" : "");

	}

	printf(" -u: Use User Fault FD to handle vCPU page faults.\n");

	printf(" -u: use User Fault FD to handle vCPU page\n"

	       "     faults.\n");

	printf(" -d: add a delay in usec to the User Fault\n"

	       "     FD handler to simulate demand paging\n"

	       "     overheads. Ignored without -u.\n");

	puts("");

	exit(0);

}
@@ -415,6 +427,7 @@ int main(int argc, char *argv[]) 
	unsigned int mode;

	int opt, i;

	bool use_uffd = false;

	useconds_t uffd_delay = 0;



#ifdef __x86_64__

	guest_mode_init(VM_MODE_PXXV48_4K, true, true);
@@ -437,7 +450,7 @@ int main(int argc, char *argv[]) 
	guest_mode_init(VM_MODE_P40V48_4K, true, true);

#endif



	while ((opt = getopt(argc, argv, "hm:u")) != -1) {

	while ((opt = getopt(argc, argv, "hm:ud:")) != -1) {

		switch (opt) {

		case 'm':

			if (!mode_selected) {
@@ -453,6 +466,11 @@ int main(int argc, char *argv[]) 
		case 'u':

			use_uffd = true;

			break;

		case 'd':

			uffd_delay = strtoul(optarg, NULL, 0);

			TEST_ASSERT(uffd_delay >= 0,

				    "A negative UFFD delay is not supported.");

			break;

		case 'h':

		default:

			help(argv[0]);
@@ -466,7 +484,7 @@ int main(int argc, char *argv[]) 
		TEST_ASSERT(guest_modes[i].supported,

			    "Guest mode ID %d (%s) not supported.",

			    i, vm_guest_mode_string(i));

		run_test(i, use_uffd);

		run_test(i, use_uffd, uffd_delay);

	}



	return 0;

CRA Git | Maintained and supported by SUSTech CRA and CCSE