On Thu, May 30, 2024 at 07:54:07PM +1000, Nicholas Piggin wrote:
> Postcopy requires userfaultfd support, which requires tmpfs if a memory
> file is used.
>
> This adds back support for /dev/shm memory files, but adds preallocation
> to skip environments where that mount is limited in size.
>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Thanks for doing this regardless.
> ---
> tests/qtest/migration-test.c | 77 ++++++++++++++++++++++++++++++++----
> 1 file changed, 69 insertions(+), 8 deletions(-)
>
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index 86eace354e..5078033ded 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -11,6 +11,7 @@
> */
>
> #include "qemu/osdep.h"
> +#include "qemu/cutils.h"
>
> #include "libqtest.h"
> #include "qapi/qmp/qdict.h"
> @@ -553,6 +554,7 @@ typedef struct {
> */
> bool hide_stderr;
> bool use_memfile;
> + bool use_shm_memfile;
Nitpick: when having both, it's slightly confusing on the name, e.g. not
clear whether use_memfile needs to be set to true too if use_shm_memfile=true.
Maybe "use_tmpfs_memfile" and "use_shm_memfile"?
> /* only launch the target process */
> bool only_target;
> /* Use dirty ring if true; dirty logging otherwise */
> @@ -739,7 +741,62 @@ static int test_migrate_start(QTestState **from,
> QTestState **to,
> ignore_stderr = "";
> }
>
> - if (args->use_memfile) {
> + if (!qtest_has_machine(machine_alias)) {
> + g_autofree char *msg = g_strdup_printf("machine %s not supported",
> + machine_alias);
> + g_test_skip(msg);
> + return -1;
> + }
> +
> + if (args->use_shm_memfile) {
> +#if defined(__NR_userfaultfd) && defined(__linux__)
IIUC we only need defined(__linux__) as there's nothing to do with uffd yet?
> + int fd;
> + uint64_t size;
> +
> + if (getenv("GITLAB_CI")) {
> + /*
> + * Gitlab runners are limited to 64MB shm size and despite
> + * pre-allocation there is concern that concurrent tests
> + * could result in nondeterministic failures. Until all shm
> + * usage in all CI tests is found to fail gracefully on
> + * ENOSPC, it is safer to avoid large allocations for now.
> + *
> + * https://lore.kernel.org/qemu-devel/875xuwg4mx....@suse.de/
> + */
> + g_test_skip("shm tests are not supported in Gitlab CI
> environment");
> + return -1;
> + }
I'm not sure whether this is Fabiano's intention. I'm wondering whether we
can drop this and just let it still run there.
Other tests not detecting avaiablility of shmem looks like a separate issue
to be fixed to me, regardless of this.
My wild guess is since we're doing memory_size+64K below then if test won't
fail others won't either, as normally the shmem quota should normally be
power of 2 anyway.. then it should always fit another few MBs if this one.
While this test is ready to fail gracefully now.
> +
> + if (!g_file_test("/dev/shm", G_FILE_TEST_IS_DIR)) {
> + g_test_skip("/dev/shm does not exist or is not a directory");
> + return -1;
> + }
> +
> + /*
> + * Pre-create and allocate the file here, because /dev/shm/
> + * is known to be limited in size in some places (e.g., Gitlab CI).
> + */
> + memfile_path = g_strdup_printf("/dev/shm/qemu-%d", getpid());
> + fd = open(memfile_path, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR |
> S_IWUSR);
> + if (fd == -1) {
> + g_test_skip("/dev/shm file could not be created");
> + return -1;
> + }
> +
> + g_assert(qemu_strtosz(memory_size, NULL, &size) == 0);
> + size += 64*1024; /* QEMU may map a bit more memory for a guard page
> */
> +
> + if (fallocate(fd, 0, 0, size) == -1) {
> + unlink(memfile_path);
> + perror("could not alloc"); exit(1);
> + g_test_skip("Could not allocate machine memory in /dev/shm");
> + return -1;
> + }
> + close(fd);
> +#else
> + g_test_skip("userfaultfd is not supported");
"/dev/shm not available" instead?
> +#endif
> + } else if (args->use_memfile) {
> memfile_path = g_strdup_printf("/%s/qemu-%d", tmpfs, getpid());
> memfile_opts = g_strdup_printf(
> "-object memory-backend-file,id=mem0,size=%s"
> @@ -751,12 +808,6 @@ static int test_migrate_start(QTestState **from,
> QTestState **to,
> kvm_opts = ",dirty-ring-size=4096";
> }
>
> - if (!qtest_has_machine(machine_alias)) {
> - g_autofree char *msg = g_strdup_printf("machine %s not supported",
> machine_alias);
> - g_test_skip(msg);
> - return -1;
> - }
> -
> machine = resolve_machine_version(machine_alias, QEMU_ENV_SRC,
> QEMU_ENV_DST);
>
> @@ -807,7 +858,7 @@ static int test_migrate_start(QTestState **from,
> QTestState **to,
> * Remove shmem file immediately to avoid memory leak in test failed
> case.
> * It's valid because QEMU has already opened this file
> */
> - if (args->use_memfile) {
> + if (args->use_memfile || args->use_shm_memfile) {
> unlink(memfile_path);
> }
>
> @@ -1275,6 +1326,15 @@ static void test_postcopy(void)
> test_postcopy_common(&args);
> }
>
> +static void test_postcopy_memfile(void)
> +{
IMHO the defined(__NR_userfaultfd) should be here to guard if needed.
Or rather, we don't need to care about uffd yet? As what we already do with
test_postcopy().
I'm guessing the test just doesn't run on !linux, while compilation always
works with/without that.
Thanks,
> + MigrateCommon args = {
> + .start.use_shm_memfile = true,
> + };
> +
> + test_postcopy_common(&args);
> +}
> +
> static void test_postcopy_suspend(void)
> {
> MigrateCommon args = {
> @@ -3441,6 +3501,7 @@ int main(int argc, char **argv)
>
> if (has_uffd) {
> migration_test_add("/migration/postcopy/plain", test_postcopy);
> + migration_test_add("/migration/postcopy/memfile",
> test_postcopy_memfile);
> migration_test_add("/migration/postcopy/recovery/plain",
> test_postcopy_recovery);
> migration_test_add("/migration/postcopy/preempt/plain",
> --
> 2.43.0
>
--
Peter Xu
