On 08/11/2019 20:49, Chris Wilson wrote:
Register a userspace fault handler for a memory region that we also pass
to the GPU via userptr, and make sure the pagefault is properly serviced
before we execute.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
tests/i915/gem_userptr_blits.c | 119 ++++++++++++++++++++++++++++++++-
1 file changed, 118 insertions(+), 1 deletion(-)
diff --git a/tests/i915/gem_userptr_blits.c b/tests/i915/gem_userptr_blits.c
index 11d6f4a1c..774a9f92c 100644
--- a/tests/i915/gem_userptr_blits.c
+++ b/tests/i915/gem_userptr_blits.c
@@ -36,6 +36,8 @@
* The goal is to simply ensure the basics work.
*/
+#include <linux/userfaultfd.h>
+
#include "igt.h"
#include <stdlib.h>
#include <stdio.h>
@@ -44,9 +46,11 @@
#include <inttypes.h>
#include <errno.h>
#include <setjmp.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
#include <sys/stat.h>
+#include <sys/syscall.h>
#include <sys/time.h>
-#include <sys/mman.h>
#include <glib.h>
#include <signal.h>
#include <pthread.h>
@@ -1831,6 +1835,116 @@ static void test_invalidate_close_race(int fd, bool overlap)
free(t_data.ptr);
}
+struct ufd_thread {
+ uint32_t *page;
+ int i915;
+};
+
+static uint32_t create_page(int i915, void *page)
+{
+ uint32_t handle;
+
+ gem_userptr(i915, page, 4096, 0, 0, &handle);
+ return handle;
+}
+
+static uint32_t create_batch(int i915)
+{
+ const uint32_t bbe = MI_BATCH_BUFFER_END;
+ uint32_t handle;
+
+ handle = gem_create(i915, 4096);
+ gem_write(i915, handle, 0, &bbe, sizeof(bbe));
+
+ return handle;
+}
+
+static void *ufd_thread(void *arg)
+{
+ struct ufd_thread *t = arg;
+ struct drm_i915_gem_exec_object2 obj[2] = {
+ { .handle = create_page(t->i915, t->page) },
+ { .handle = create_batch(t->i915) },
+ };
+ struct drm_i915_gem_execbuffer2 eb = {
+ .buffers_ptr = to_user_pointer(obj),
+ .buffer_count = ARRAY_SIZE(obj),
+ };
+
+ igt_debug("submitting fault\n");
+ gem_execbuf(t->i915, &eb);
+ gem_sync(t->i915, obj[1].handle);
+
+ for (int i = 0; i < ARRAY_SIZE(obj); i++)
+ gem_close(t->i915, obj[i].handle);
+
+ t->i915 = -1;
+ return NULL;
+}
+
+static int userfaultfd(int flags)
+{
+ return syscall(SYS_userfaultfd, flags);
+}
+
+static void test_userfault(int i915)
+{
+ struct uffdio_api api = { .api = UFFD_API };
+ struct uffdio_register reg;
+ struct uffdio_copy copy;
+ struct uffd_msg msg;
+ struct ufd_thread t;
+ pthread_t thread;
+ char poison[4096];
+ int ufd;
+
+ /*
+ * Register a page with userfaultfd, and wrap that inside a userptr bo.
+ * When we try to use gup insider userptr_get_pages, it will trigger
+ * a pagefault that is sent to the userfaultfd for servicing. This
+ * is arbitrarily slow, as the submission must wait until the fault
+ * is serviced by the userspace fault handler.
+ */
+
+ ufd = userfaultfd(0);
+ igt_require_f(ufd != -1, "kernel support for userfaultfd\n");
+ igt_require_f(ioctl(ufd, UFFDIO_API, &api) == 0 && api.api == UFFD_API,
+ "userfaultfd API v%lld:%lld\n", UFFD_API, api.api);
+
+ t.i915 = i915;
+
+ t.page = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, 0, 0);
+ igt_assert(t.page != MAP_FAILED);
+
+ memset(®, 0, sizeof(reg));
+ reg.mode = UFFDIO_REGISTER_MODE_MISSING;
+ reg.range.start = to_user_pointer(t.page);
+ reg.range.len = 4096;
+ do_ioctl(ufd, UFFDIO_REGISTER, ®);
+ igt_assert(reg.ioctls == UFFD_API_RANGE_IOCTLS);
+
+ igt_assert(pthread_create(&thread, NULL, ufd_thread, &t) == 0);
+
+ /* Wait for the fault */
+ igt_assert_eq(read(ufd, &msg, sizeof(msg)), sizeof(msg));
+ igt_assert_eq(msg.event, UFFD_EVENT_PAGEFAULT);
+ igt_assert(from_user_pointer(msg.arg.pagefault.address) == t.page);
+
+ /* Faulting thread remains blocked */
+ igt_assert_eq(t.i915, i915);
This looks could be a false negative since nothing says the thread is
not blocked just not got round resetting t->i915.
+
+ memset(©, 0, sizeof(copy));
+ copy.dst = msg.arg.pagefault.address;
+ copy.src = to_user_pointer(memset(poison, 0xc5, sizeof(poison)));
+ copy.len = 4096;
+ do_ioctl(ufd, UFFDIO_COPY, ©);
What is the point of poison data?
Would it work better to have a hanging batch registered with userfault
and then replace it with a valid batch here? That would ensure execbuf
was blocked until userfault handler finishes otherwise we get a GPU hang.
Regards,
Tvrtko
+
+ pthread_join(thread, NULL);
+
+ munmap(t.page, 4096);
+ close(ufd);
+}
+
uint64_t total_ram;
uint64_t aperture_size;
int fd, count;
@@ -1902,6 +2016,9 @@ igt_main_args("c:", NULL, help_str, opt_handler, NULL)
igt_subtest("forbidden-operations")
test_forbidden_ops(fd);
+ igt_subtest("userfault")
+ test_userfault(fd);
+
igt_subtest("relocations")
test_relocations(fd);
}
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