diff mbox series

[v5,3/5] userfaultfd: selftests: modify selftest to use /dev/userfaultfd

Message ID 20220808175614.3885028-4-axelrasmussen@google.com (mailing list archive)
State New, archived
Headers show
Series userfaultfd: add /dev/userfaultfd for fine grained access control | expand

Commit Message

Axel Rasmussen Aug. 8, 2022, 5:56 p.m. UTC
We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
working into the future, so just run the test twice, using each
interface.

Instead of always testing both userfaultfd(2) and /dev/userfaultfd,
let the user choose which to test.

As with other test features, change the behavior based on a new
command line flag. Introduce the idea of "test mods", which are
generic (not specific to a test type) modifications to the behavior of
the test. This is sort of borrowed from this RFC patch series [1], but
simplified a bit.

The benefit is, in "typical" configurations this test is somewhat slow
(say, 30sec or something). Testing both clearly doubles it, so it may
not always be desirable, as users are likely to use one or the other,
but never both, in the "real world".

[1]: https://patchwork.kernel.org/project/linux-mm/patch/20201129004548.1619714-14-namit@vmware.com/

Acked-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
 tools/testing/selftests/vm/userfaultfd.c | 69 ++++++++++++++++++++----
 1 file changed, 60 insertions(+), 9 deletions(-)

Comments

Mike Rapoport Aug. 11, 2022, 6:38 a.m. UTC | #1
On Mon, Aug 08, 2022 at 10:56:12AM -0700, Axel Rasmussen wrote:
> We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
> working into the future, so just run the test twice, using each
> interface.
> 
> Instead of always testing both userfaultfd(2) and /dev/userfaultfd,
> let the user choose which to test.
> 
> As with other test features, change the behavior based on a new
> command line flag. Introduce the idea of "test mods", which are
> generic (not specific to a test type) modifications to the behavior of
> the test. This is sort of borrowed from this RFC patch series [1], but
> simplified a bit.
> 
> The benefit is, in "typical" configurations this test is somewhat slow
> (say, 30sec or something). Testing both clearly doubles it, so it may
> not always be desirable, as users are likely to use one or the other,
> but never both, in the "real world".
> 
> [1]: https://patchwork.kernel.org/project/linux-mm/patch/20201129004548.1619714-14-namit@vmware.com/
> 
> Acked-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>

With a few nits below

Acked-by: Mike Rapoport <rppt@linux.ibm.com>

> ---
>  tools/testing/selftests/vm/userfaultfd.c | 69 ++++++++++++++++++++----
>  1 file changed, 60 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 7c3f1b0ab468..cae72867c173 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -77,6 +77,11 @@ static int bounces;
>  #define TEST_SHMEM	3
>  static int test_type;
>  
> +#define UFFD_FLAGS	(O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY)
> +
> +/* test using /dev/userfaultfd, instead of userfaultfd(2) */
> +static bool test_dev_userfaultfd;
> +
>  /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
>  #define ALARM_INTERVAL_SECS 10
>  static volatile bool test_uffdio_copy_eexist = true;
> @@ -125,6 +130,8 @@ struct uffd_stats {
>  const char *examples =
>      "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
>      "./userfaultfd anon 100 99999\n\n"
> +    "# Run the same anonymous memory test, but using /dev/userfaultfd:\n"
> +    "./userfaultfd anon:dev 100 99999\n\n"
>      "# Run share memory test on 1GiB region with 99 bounces:\n"
>      "./userfaultfd shmem 1000 99\n\n"
>      "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
> @@ -141,6 +148,14 @@ static void usage(void)
>  		"[hugetlbfs_file]\n\n");
>  	fprintf(stderr, "Supported <test type>: anon, hugetlb, "
>  		"hugetlb_shared, shmem\n\n");
> +	fprintf(stderr, "'Test mods' can be joined to the test type string with a ':'. "
> +		"Supported mods:\n");
> +	fprintf(stderr, "\tsyscall - Use userfaultfd(2) (default)\n");
> +	fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
> +	fprintf(stderr, "\nExample test mod usage:\n");
> +	fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
> +	fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
> +
>  	fprintf(stderr, "Examples:\n\n");
>  	fprintf(stderr, "%s", examples);
>  	exit(1);
> @@ -154,12 +169,14 @@ static void usage(void)
>  			ret, __LINE__);				\
>  	} while (0)
>  
> -#define err(fmt, ...)				\
> +#define errexit(exitcode, fmt, ...)		\
>  	do {					\
>  		_err(fmt, ##__VA_ARGS__);	\
> -		exit(1);			\
> +		exit(exitcode);			\
>  	} while (0)
>  
> +#define err(fmt, ...) errexit(1, fmt, ##__VA_ARGS__)
> +
>  static void uffd_stats_reset(struct uffd_stats *uffd_stats,
>  			     unsigned long n_cpus)
>  {
> @@ -383,13 +400,29 @@ static void assert_expected_ioctls_present(uint64_t mode, uint64_t ioctls)
>  	}
>  }
>  
> +static int __userfaultfd_open_dev(void)
> +{
> +	int fd, _uffd = -1;

Nit: the initialization here is not necessary, _uffd is always set from
ioctl() return value.

> +
> +	fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
> +	if (fd < 0)
> +		return -1;
> +
> +	_uffd = ioctl(fd, USERFAULTFD_IOC_NEW, UFFD_FLAGS);
> +	close(fd);
> +	return _uffd;
> +}
> +
>  static void userfaultfd_open(uint64_t *features)
>  {
>  	struct uffdio_api uffdio_api;
>  
> -	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
> +	if (test_dev_userfaultfd)
> +		uffd = __userfaultfd_open_dev();
> +	else
> +		uffd = syscall(__NR_userfaultfd, UFFD_FLAGS);
>  	if (uffd < 0)
> -		err("userfaultfd syscall not available in this kernel");
> +		errexit(KSFT_SKIP, "creating userfaultfd failed");

I'm not sure if this should be KSFT_SKIP. If creation of uffd failed
because anything except ENOSYS I'd consider the test failing. 

>  	uffd_flags = fcntl(uffd, F_GETFD, NULL);
>  
>  	uffdio_api.api = UFFD_API;
> @@ -1584,8 +1617,6 @@ unsigned long default_huge_page_size(void)
>  
>  static void set_test_type(const char *type)
>  {
> -	uint64_t features = UFFD_API_FEATURES;
> -
>  	if (!strcmp(type, "anon")) {
>  		test_type = TEST_ANON;
>  		uffd_test_ops = &anon_uffd_test_ops;
> @@ -1603,9 +1634,29 @@ static void set_test_type(const char *type)
>  		test_type = TEST_SHMEM;
>  		uffd_test_ops = &shmem_uffd_test_ops;
>  		test_uffdio_minor = true;
> -	} else {
> -		err("Unknown test type: %s", type);
>  	}
> +}
> +
> +static void parse_test_type_arg(const char *raw_type)
> +{
> +	char *buf = strdup(raw_type);
> +	uint64_t features = UFFD_API_FEATURES;
> +
> +	while (buf) {
> +		const char *token = strsep(&buf, ":");
> +
> +		if (!test_type)
> +			set_test_type(token);
> +		else if (!strcmp(token, "dev"))
> +			test_dev_userfaultfd = true;
> +		else if (!strcmp(token, "syscall"))
> +			test_dev_userfaultfd = false;
> +		else
> +			err("unrecognized test mod '%s'", token);
> +	}
> +
> +	if (!test_type)
> +		err("failed to parse test type argument: '%s'", raw_type);
>  
>  	if (test_type == TEST_HUGETLB)
>  		page_size = default_huge_page_size();
> @@ -1653,7 +1704,7 @@ int main(int argc, char **argv)
>  		err("failed to arm SIGALRM");
>  	alarm(ALARM_INTERVAL_SECS);
>  
> -	set_test_type(argv[1]);
> +	parse_test_type_arg(argv[1]);
>  
>  	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
>  	nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
> -- 
> 2.37.1.559.g78731f0fdb-goog
>
Axel Rasmussen Aug. 17, 2022, 7:53 p.m. UTC | #2
On Wed, Aug 10, 2022 at 11:38 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> On Mon, Aug 08, 2022 at 10:56:12AM -0700, Axel Rasmussen wrote:
> > We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
> > working into the future, so just run the test twice, using each
> > interface.
> >
> > Instead of always testing both userfaultfd(2) and /dev/userfaultfd,
> > let the user choose which to test.
> >
> > As with other test features, change the behavior based on a new
> > command line flag. Introduce the idea of "test mods", which are
> > generic (not specific to a test type) modifications to the behavior of
> > the test. This is sort of borrowed from this RFC patch series [1], but
> > simplified a bit.
> >
> > The benefit is, in "typical" configurations this test is somewhat slow
> > (say, 30sec or something). Testing both clearly doubles it, so it may
> > not always be desirable, as users are likely to use one or the other,
> > but never both, in the "real world".
> >
> > [1]: https://patchwork.kernel.org/project/linux-mm/patch/20201129004548.1619714-14-namit@vmware.com/
> >
> > Acked-by: Peter Xu <peterx@redhat.com>
> > Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
>
> With a few nits below
>
> Acked-by: Mike Rapoport <rppt@linux.ibm.com>

Thanks for reviewing, Mike!

>
> > ---
> >  tools/testing/selftests/vm/userfaultfd.c | 69 ++++++++++++++++++++----
> >  1 file changed, 60 insertions(+), 9 deletions(-)
> >
> > diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> > index 7c3f1b0ab468..cae72867c173 100644
> > --- a/tools/testing/selftests/vm/userfaultfd.c
> > +++ b/tools/testing/selftests/vm/userfaultfd.c
> > @@ -77,6 +77,11 @@ static int bounces;
> >  #define TEST_SHMEM   3
> >  static int test_type;
> >
> > +#define UFFD_FLAGS   (O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY)
> > +
> > +/* test using /dev/userfaultfd, instead of userfaultfd(2) */
> > +static bool test_dev_userfaultfd;
> > +
> >  /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
> >  #define ALARM_INTERVAL_SECS 10
> >  static volatile bool test_uffdio_copy_eexist = true;
> > @@ -125,6 +130,8 @@ struct uffd_stats {
> >  const char *examples =
> >      "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
> >      "./userfaultfd anon 100 99999\n\n"
> > +    "# Run the same anonymous memory test, but using /dev/userfaultfd:\n"
> > +    "./userfaultfd anon:dev 100 99999\n\n"
> >      "# Run share memory test on 1GiB region with 99 bounces:\n"
> >      "./userfaultfd shmem 1000 99\n\n"
> >      "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
> > @@ -141,6 +148,14 @@ static void usage(void)
> >               "[hugetlbfs_file]\n\n");
> >       fprintf(stderr, "Supported <test type>: anon, hugetlb, "
> >               "hugetlb_shared, shmem\n\n");
> > +     fprintf(stderr, "'Test mods' can be joined to the test type string with a ':'. "
> > +             "Supported mods:\n");
> > +     fprintf(stderr, "\tsyscall - Use userfaultfd(2) (default)\n");
> > +     fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
> > +     fprintf(stderr, "\nExample test mod usage:\n");
> > +     fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
> > +     fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
> > +
> >       fprintf(stderr, "Examples:\n\n");
> >       fprintf(stderr, "%s", examples);
> >       exit(1);
> > @@ -154,12 +169,14 @@ static void usage(void)
> >                       ret, __LINE__);                         \
> >       } while (0)
> >
> > -#define err(fmt, ...)                                \
> > +#define errexit(exitcode, fmt, ...)          \
> >       do {                                    \
> >               _err(fmt, ##__VA_ARGS__);       \
> > -             exit(1);                        \
> > +             exit(exitcode);                 \
> >       } while (0)
> >
> > +#define err(fmt, ...) errexit(1, fmt, ##__VA_ARGS__)
> > +
> >  static void uffd_stats_reset(struct uffd_stats *uffd_stats,
> >                            unsigned long n_cpus)
> >  {
> > @@ -383,13 +400,29 @@ static void assert_expected_ioctls_present(uint64_t mode, uint64_t ioctls)
> >       }
> >  }
> >
> > +static int __userfaultfd_open_dev(void)
> > +{
> > +     int fd, _uffd = -1;
>
> Nit: the initialization here is not necessary, _uffd is always set from
> ioctl() return value.

Agreed.

>
> > +
> > +     fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
> > +     if (fd < 0)
> > +             return -1;
> > +
> > +     _uffd = ioctl(fd, USERFAULTFD_IOC_NEW, UFFD_FLAGS);
> > +     close(fd);
> > +     return _uffd;
> > +}
> > +
> >  static void userfaultfd_open(uint64_t *features)
> >  {
> >       struct uffdio_api uffdio_api;
> >
> > -     uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
> > +     if (test_dev_userfaultfd)
> > +             uffd = __userfaultfd_open_dev();
> > +     else
> > +             uffd = syscall(__NR_userfaultfd, UFFD_FLAGS);
> >       if (uffd < 0)
> > -             err("userfaultfd syscall not available in this kernel");
> > +             errexit(KSFT_SKIP, "creating userfaultfd failed");
>
> I'm not sure if this should be KSFT_SKIP. If creation of uffd failed
> because anything except ENOSYS I'd consider the test failing.

Agreed, but looking at it I think it's more complicated.

In __userfaultfd_open_dev, I think:
- If we fail to open /dev/userfaultfd for any reason, that's a KSFT_SKIP
- If USERFAULTFD_IOC_NEW returns ENOTTY that's a KSFT_SKIP, otherwise
a real test failure.

But then for syscall(__NR_userfaultfd, ...), I think ENOSYS is a
KSFT_SKIP, but any other errno is a real test failure.

I'll send an updated version which has those semantics. I think to do
so we need to move some of the error handling into
__userfaultfd_open_dev, instead of having its caller do it.

>
> >       uffd_flags = fcntl(uffd, F_GETFD, NULL);
> >
> >       uffdio_api.api = UFFD_API;
> > @@ -1584,8 +1617,6 @@ unsigned long default_huge_page_size(void)
> >
> >  static void set_test_type(const char *type)
> >  {
> > -     uint64_t features = UFFD_API_FEATURES;
> > -
> >       if (!strcmp(type, "anon")) {
> >               test_type = TEST_ANON;
> >               uffd_test_ops = &anon_uffd_test_ops;
> > @@ -1603,9 +1634,29 @@ static void set_test_type(const char *type)
> >               test_type = TEST_SHMEM;
> >               uffd_test_ops = &shmem_uffd_test_ops;
> >               test_uffdio_minor = true;
> > -     } else {
> > -             err("Unknown test type: %s", type);
> >       }
> > +}
> > +
> > +static void parse_test_type_arg(const char *raw_type)
> > +{
> > +     char *buf = strdup(raw_type);
> > +     uint64_t features = UFFD_API_FEATURES;
> > +
> > +     while (buf) {
> > +             const char *token = strsep(&buf, ":");
> > +
> > +             if (!test_type)
> > +                     set_test_type(token);
> > +             else if (!strcmp(token, "dev"))
> > +                     test_dev_userfaultfd = true;
> > +             else if (!strcmp(token, "syscall"))
> > +                     test_dev_userfaultfd = false;
> > +             else
> > +                     err("unrecognized test mod '%s'", token);
> > +     }
> > +
> > +     if (!test_type)
> > +             err("failed to parse test type argument: '%s'", raw_type);
> >
> >       if (test_type == TEST_HUGETLB)
> >               page_size = default_huge_page_size();
> > @@ -1653,7 +1704,7 @@ int main(int argc, char **argv)
> >               err("failed to arm SIGALRM");
> >       alarm(ALARM_INTERVAL_SECS);
> >
> > -     set_test_type(argv[1]);
> > +     parse_test_type_arg(argv[1]);
> >
> >       nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> >       nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
> > --
> > 2.37.1.559.g78731f0fdb-goog
> >
>
> --
> Sincerely yours,
> Mike.
diff mbox series

Patch

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 7c3f1b0ab468..cae72867c173 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -77,6 +77,11 @@  static int bounces;
 #define TEST_SHMEM	3
 static int test_type;
 
+#define UFFD_FLAGS	(O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY)
+
+/* test using /dev/userfaultfd, instead of userfaultfd(2) */
+static bool test_dev_userfaultfd;
+
 /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
 #define ALARM_INTERVAL_SECS 10
 static volatile bool test_uffdio_copy_eexist = true;
@@ -125,6 +130,8 @@  struct uffd_stats {
 const char *examples =
     "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
     "./userfaultfd anon 100 99999\n\n"
+    "# Run the same anonymous memory test, but using /dev/userfaultfd:\n"
+    "./userfaultfd anon:dev 100 99999\n\n"
     "# Run share memory test on 1GiB region with 99 bounces:\n"
     "./userfaultfd shmem 1000 99\n\n"
     "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
@@ -141,6 +148,14 @@  static void usage(void)
 		"[hugetlbfs_file]\n\n");
 	fprintf(stderr, "Supported <test type>: anon, hugetlb, "
 		"hugetlb_shared, shmem\n\n");
+	fprintf(stderr, "'Test mods' can be joined to the test type string with a ':'. "
+		"Supported mods:\n");
+	fprintf(stderr, "\tsyscall - Use userfaultfd(2) (default)\n");
+	fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
+	fprintf(stderr, "\nExample test mod usage:\n");
+	fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
+	fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
+
 	fprintf(stderr, "Examples:\n\n");
 	fprintf(stderr, "%s", examples);
 	exit(1);
@@ -154,12 +169,14 @@  static void usage(void)
 			ret, __LINE__);				\
 	} while (0)
 
-#define err(fmt, ...)				\
+#define errexit(exitcode, fmt, ...)		\
 	do {					\
 		_err(fmt, ##__VA_ARGS__);	\
-		exit(1);			\
+		exit(exitcode);			\
 	} while (0)
 
+#define err(fmt, ...) errexit(1, fmt, ##__VA_ARGS__)
+
 static void uffd_stats_reset(struct uffd_stats *uffd_stats,
 			     unsigned long n_cpus)
 {
@@ -383,13 +400,29 @@  static void assert_expected_ioctls_present(uint64_t mode, uint64_t ioctls)
 	}
 }
 
+static int __userfaultfd_open_dev(void)
+{
+	int fd, _uffd = -1;
+
+	fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		return -1;
+
+	_uffd = ioctl(fd, USERFAULTFD_IOC_NEW, UFFD_FLAGS);
+	close(fd);
+	return _uffd;
+}
+
 static void userfaultfd_open(uint64_t *features)
 {
 	struct uffdio_api uffdio_api;
 
-	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
+	if (test_dev_userfaultfd)
+		uffd = __userfaultfd_open_dev();
+	else
+		uffd = syscall(__NR_userfaultfd, UFFD_FLAGS);
 	if (uffd < 0)
-		err("userfaultfd syscall not available in this kernel");
+		errexit(KSFT_SKIP, "creating userfaultfd failed");
 	uffd_flags = fcntl(uffd, F_GETFD, NULL);
 
 	uffdio_api.api = UFFD_API;
@@ -1584,8 +1617,6 @@  unsigned long default_huge_page_size(void)
 
 static void set_test_type(const char *type)
 {
-	uint64_t features = UFFD_API_FEATURES;
-
 	if (!strcmp(type, "anon")) {
 		test_type = TEST_ANON;
 		uffd_test_ops = &anon_uffd_test_ops;
@@ -1603,9 +1634,29 @@  static void set_test_type(const char *type)
 		test_type = TEST_SHMEM;
 		uffd_test_ops = &shmem_uffd_test_ops;
 		test_uffdio_minor = true;
-	} else {
-		err("Unknown test type: %s", type);
 	}
+}
+
+static void parse_test_type_arg(const char *raw_type)
+{
+	char *buf = strdup(raw_type);
+	uint64_t features = UFFD_API_FEATURES;
+
+	while (buf) {
+		const char *token = strsep(&buf, ":");
+
+		if (!test_type)
+			set_test_type(token);
+		else if (!strcmp(token, "dev"))
+			test_dev_userfaultfd = true;
+		else if (!strcmp(token, "syscall"))
+			test_dev_userfaultfd = false;
+		else
+			err("unrecognized test mod '%s'", token);
+	}
+
+	if (!test_type)
+		err("failed to parse test type argument: '%s'", raw_type);
 
 	if (test_type == TEST_HUGETLB)
 		page_size = default_huge_page_size();
@@ -1653,7 +1704,7 @@  int main(int argc, char **argv)
 		err("failed to arm SIGALRM");
 	alarm(ALARM_INTERVAL_SECS);
 
-	set_test_type(argv[1]);
+	parse_test_type_arg(argv[1]);
 
 	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
 	nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /