Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Performing a GPU reset clobbers the fence registers, affecting which
> addresses the tiled GTT mmap access. If the driver does not take
> precautions across a GPU reset, a client may read the wrong values (but
> only within their own buffer as the fence will only be degraded to
> I915_TILING_NONE, reducing the access area). However, as this requires
> performing a read using the indirect GTT at exactly the same time as the
> reset occurs, it can be quite difficult to catch, so repeat the test
> many times and across all cores simultaneously.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> tests/i915/gem_mmap_gtt.c | 99 +++++++++++++++++++++++++++------------
> 1 file changed, 68 insertions(+), 31 deletions(-)
>
> diff --git a/tests/i915/gem_mmap_gtt.c b/tests/i915/gem_mmap_gtt.c
> index f63535556..21880d31d 100644
> --- a/tests/i915/gem_mmap_gtt.c
> +++ b/tests/i915/gem_mmap_gtt.c
> @@ -38,6 +38,7 @@
> #include "drm.h"
>
> #include "igt.h"
> +#include "igt_sysfs.h"
> #include "igt_x86.h"
>
> #ifndef PAGE_SIZE
> @@ -375,50 +376,86 @@ test_clflush(int fd)
> static void
> test_hang(int fd)
> {
> - igt_hang_t hang;
> - uint32_t patterns[] = {
> + const uint32_t patterns[] = {
> 0, 0xaaaaaaaa, 0x55555555, 0xcccccccc,
> };
> - uint32_t *gtt[3];
> - int last_pattern = 0;
> - int next_pattern = 1;
> - int i;
> + const int ncpus = sysconf(_SC_NPROCESSORS_ONLN);
> + struct {
> + bool done;
> + bool error;
> + } *control;
> + unsigned long count;
> + igt_hang_t hang;
> + int dir;
>
> - for (i = I915_TILING_NONE; i <= I915_TILING_Y; i++) {
> - uint32_t handle;
> + hang = igt_allow_hang(fd, 0, 0);
> + igt_sysfs_set_parameter(fd, "reset", "1"); /* global resets */
igt_assert to be sure that you made it?
igt_sysfs_set_module_parameter would be less misleadning :P
>
> - handle = gem_create(fd, OBJECT_SIZE);
> - gem_set_tiling(fd, handle, i, 2048);
> + control = mmap(NULL, 4096, PROT_WRITE, MAP_SHARED | MAP_ANON, -1, 0);
> + igt_assert(control != MAP_FAILED);
>
> - gtt[i] = gem_mmap__gtt(fd, handle, OBJECT_SIZE, PROT_WRITE);
> - set_domain_gtt(fd, handle);
> - gem_close(fd, handle);
> - }
> + igt_fork(child, ncpus) {
> + int last_pattern = 0;
> + int next_pattern = 1;
> + uint32_t *gtt[2];
You throw tiling none out as it is just a distraction and
waste of cycles?
>
> - hang = igt_hang_ring(fd, I915_EXEC_RENDER);
> + for (int i = 0; i < ARRAY_SIZE(gtt); i++) {
> + uint32_t handle;
>
> - do {
> - for (i = 0; i < OBJECT_SIZE / 64; i++) {
> - int x = 16*i + (i%16);
> + handle = gem_create(fd, OBJECT_SIZE);
> + gem_set_tiling(fd, handle, I915_TILING_X + i, 2048);
You could have setup a priori. But this prolly is faster than
one reset cycle of tests so nothing to gain.
>
> - igt_assert(gtt[0][x] == patterns[last_pattern]);
> - igt_assert(gtt[1][x] == patterns[last_pattern]);
> - igt_assert(gtt[2][x] == patterns[last_pattern]);
> + gtt[i] = gem_mmap__gtt(fd, handle, OBJECT_SIZE, PROT_WRITE);
> + set_domain_gtt(fd, handle);
> + gem_close(fd, handle);
> + }
>
> - gtt[0][x] = patterns[next_pattern];
> - gtt[1][x] = patterns[next_pattern];
> - gtt[2][x] = patterns[next_pattern];
> + while (!READ_ONCE(control->done)) {
> + for (int i = 0; i < OBJECT_SIZE / 64; i++) {
> + uint32_t expected = patterns[last_pattern];
> + uint32_t found[2];
> + int x = 16*i + (i%16);
nitpicking here for consts and unsigned x.
> +
> + found[0] = READ_ONCE(gtt[0][x]);
> + found[1] = READ_ONCE(gtt[1][x]);
> +
> + if (found[0] != expected ||
> + found[1] != expected) {
> + igt_warn("child[%d] found (%x, %x), expecting %x\n",
> + child,
> + found[0], found[1],
> + expected);
> + control->error = true;
> + exit(0);
> + }
> +
> + gtt[0][x] = patterns[next_pattern];
> + gtt[1][x] = patterns[next_pattern];
> + }
> +
> + last_pattern = next_pattern;
> + next_pattern = (next_pattern + 1) % ARRAY_SIZE(patterns);
> }
> + }
>
> - last_pattern = next_pattern;
> - next_pattern = (next_pattern + 1) % ARRAY_SIZE(patterns);
> - } while (gem_bo_busy(fd, hang.spin->handle));
Well, no concern here anymore that something would sync on
there.
Only nitpicks so,
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> + count = 0;
> + dir = igt_debugfs_dir(fd);
> + igt_until_timeout(5) {
> + igt_sysfs_set(dir, "i915_wedged", "-1");
> + if (READ_ONCE(control->error))
> + break;
> + count++;
> + }
> + close(dir);
> + igt_info("%lu resets\n", count);
> +
> + control->done = true;
> + igt_waitchildren();
>
> - igt_post_hang_ring(fd, hang);
> + igt_assert(!control->error);
> + munmap(control, 4096);
>
> - munmap(gtt[0], OBJECT_SIZE);
> - munmap(gtt[1], OBJECT_SIZE);
> - munmap(gtt[2], OBJECT_SIZE);
> + igt_disallow_hang(fd, hang);
> }
>
> static int min_tile_width(uint32_t devid, int tiling)
> --
> 2.20.1
>
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