Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> intel_timeline_read_hwsp() is used to support semaphore waits between
> engines, that may themselves be deferred for arbitrary periods -- that
> is the read of the target request's HWSP is at an indeterminant point in
> the future. To support this, we need to prevent overwriting a HWSP that
> is being watched across a seqno wrap (otherwise the next request will
> write its value into the old HWSP preventing the watcher from making
> progress, ad infinitum.) To simulate the observer across a wrap, let's
> create a request that reads from the HWSP and dispatch it at different
> points around a wrap to see if the value is lost.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/selftest_timeline.c | 378 +++++++++++++++++++-
> 1 file changed, 376 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_timeline.c b/drivers/gpu/drm/i915/gt/selftest_timeline.c
> index 19c2cb166e7c..2edf2b15885f 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_timeline.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_timeline.c
> @@ -17,8 +17,9 @@
> #include "../selftests/i915_random.h"
> #include "../i915_selftest.h"
>
> -#include "../selftests/igt_flush_test.h"
> -#include "../selftests/mock_gem_device.h"
> +#include "selftests/igt_flush_test.h"
> +#include "selftests/lib_sw_fence.h"
> +#include "selftests/mock_gem_device.h"
> #include "selftests/mock_timeline.h"
>
> static struct page *hwsp_page(struct intel_timeline *tl)
> @@ -755,6 +756,378 @@ static int live_hwsp_wrap(void *arg)
> return err;
> }
>
> +static int emit_read_hwsp(struct i915_request *rq,
> + u32 seqno, u32 hwsp,
> + u32 *addr)
> +{
> + const u32 gpr = i915_mmio_reg_offset(GEN8_RING_CS_GPR(rq->engine->mmio_base, 0));
> + u32 *cs;
> +
> + cs = intel_ring_begin(rq, 12);
> + if (IS_ERR(cs))
> + return PTR_ERR(cs);
> +
> + *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
> + *cs++ = *addr;
> + *cs++ = 0;
> + *cs++ = seqno;
> + *addr += 4;
> +
> + *cs++ = MI_LOAD_REGISTER_MEM_GEN8 | MI_USE_GGTT;
> + *cs++ = gpr;
> + *cs++ = hwsp;
> + *cs++ = 0;
> +
> + *cs++ = MI_STORE_REGISTER_MEM_GEN8 | MI_USE_GGTT;
> + *cs++ = gpr;
> + *cs++ = *addr;
> + *cs++ = 0;
> + *addr += 4;
> +
> + intel_ring_advance(rq, cs);
> +
> + return 0;
> +}
> +
> +struct hwsp_watcher {
> + struct i915_vma *vma;
> + struct i915_request *rq;
> + u32 addr;
> + u32 *map;
> +};
> +
> +static bool cmp_lt(u32 a, u32 b)
> +{
> + return a < b;
> +}
> +
> +static bool cmp_gte(u32 a, u32 b)
> +{
> + return a >= b;
> +}
> +
> +static int setup_watcher(struct hwsp_watcher *w, struct intel_gt *gt)
> +{
> + struct drm_i915_gem_object *obj;
> + struct i915_vma *vma;
> +
> + obj = i915_gem_object_create_internal(gt->i915, SZ_2M);
> + if (IS_ERR(obj))
> + return PTR_ERR(obj);
> +
> + w->map = i915_gem_object_pin_map(obj, I915_MAP_WB);
> + if (IS_ERR(w->map)) {
> + i915_gem_object_put(obj);
> + return PTR_ERR(w->map);
> + }
> +
> + vma = i915_gem_object_ggtt_pin_ww(obj, NULL, NULL, 0, 0, 0);
> + if (IS_ERR(vma)) {
> + i915_gem_object_put(obj);
> + return PTR_ERR(vma);
> + }
> +
> + w->vma = vma;
> + w->addr = i915_ggtt_offset(vma);
> + return 0;
> +}
> +
> +static int create_watcher(struct hwsp_watcher *w,
> + struct intel_engine_cs *engine,
> + int ringsz)
> +{
> + struct intel_context *ce;
> + struct intel_timeline *tl;
> +
> + ce = intel_context_create(engine);
> + if (IS_ERR(ce))
> + return PTR_ERR(ce);
> +
> + ce->ring = __intel_context_ring_size(ringsz);
> + w->rq = intel_context_create_request(ce);
> + intel_context_put(ce);
> + if (IS_ERR(w->rq))
> + return PTR_ERR(w->rq);
> +
> + w->addr = i915_ggtt_offset(w->vma);
> + tl = w->rq->context->timeline;
> +
> + /* some light mutex juggling required; think co-routines */
> + lockdep_unpin_lock(&tl->mutex, w->rq->cookie);
> + mutex_unlock(&tl->mutex);
> +
> + return 0;
> +}
> +
> +static int check_watcher(struct hwsp_watcher *w, const char *name,
> + bool (*op)(u32 hwsp, u32 seqno))
> +{
> + struct i915_request *rq = fetch_and_zero(&w->rq);
> + struct intel_timeline *tl = rq->context->timeline;
> + u32 offset, end;
> + int err;
> +
> + GEM_BUG_ON(w->addr - i915_ggtt_offset(w->vma) > w->vma->size);
> +
> + i915_request_get(rq);
> + mutex_lock(&tl->mutex);
> + rq->cookie = lockdep_pin_lock(&tl->mutex);
> + i915_request_add(rq);
> +
> + if (i915_request_wait(rq, 0, HZ) < 0) {
> + err = -ETIME;
> + goto out;
> + }
> +
> + err = 0;
> + offset = 0;
> + end = (w->addr - i915_ggtt_offset(w->vma)) / sizeof(*w->map);
> + while (offset < end) {
> + if (!op(w->map[offset + 1], w->map[offset])) {
> + pr_err("Watcher '%s' found HWSP value %x for seqno %x\n",
> + name, w->map[offset + 1], w->map[offset]);
> + err = -EINVAL;
> + }
> +
> + offset += 2;
> + }
> +
> +out:
> + i915_request_put(rq);
> + return err;
> +}
> +
> +static void cleanup_watcher(struct hwsp_watcher *w)
> +{
> + if (w->rq) {
> + struct intel_timeline *tl = w->rq->context->timeline;
> +
> + mutex_lock(&tl->mutex);
> + w->rq->cookie = lockdep_pin_lock(&tl->mutex);
> +
> + i915_request_add(w->rq);
> + }
> +
> + i915_vma_unpin_and_release(&w->vma, I915_VMA_RELEASE_MAP);
> +}
> +
> +static bool retire_requests(struct intel_timeline *tl)
> +{
> + struct i915_request *rq, *rn;
> +
> + mutex_lock(&tl->mutex);
> + list_for_each_entry_safe(rq, rn, &tl->requests, link)
> + if (!i915_request_retire(rq))
> + break;
> + mutex_unlock(&tl->mutex);
> +
> + return !i915_active_fence_isset(&tl->last_request);
> +}
> +
> +static struct i915_request *wrap_timeline(struct i915_request *rq)
> +{
> + struct intel_context *ce = rq->context;
> + struct intel_timeline *tl = ce->timeline;
> + u32 seqno = rq->fence.seqno;
> +
> + while (tl->seqno >= seqno) { /* Cause a wrap */
> + i915_request_put(rq);
> + rq = intel_context_create_request(ce);
> + if (IS_ERR(rq))
> + return rq;
> +
> + i915_request_get(rq);
> + i915_request_add(rq);
> + }
> +
> + i915_request_put(rq);
> + rq = intel_context_create_request(ce);
> + if (IS_ERR(rq))
> + return rq;
> +
> + i915_request_get(rq);
> + i915_request_add(rq);
> +
> + return rq;
> +}
> +
> +static int live_hwsp_read(void *arg)
> +{
> + struct intel_gt *gt = arg;
> + struct hwsp_watcher watcher[2] = {};
> + struct intel_engine_cs *engine;
> + struct intel_timeline *tl;
> + enum intel_engine_id id;
> + int err = 0;
> + int i;
> +
> + /*
> + * If we take a reference to the HWSP for reading on the GPU, that
> + * read may be arbitrarily delayed (either by foreign fence or
> + * priority saturation) and a wrap can happen within 30 minutes.
> + * When the GPU read is finally submitted it should be correct,
> + * even across multiple wraps.
> + */
> +
> + if (INTEL_GEN(gt->i915) < 8) /* CS convenience [SRM/LRM] */
> + return 0;
> +
> + tl = intel_timeline_create(gt);
> + if (IS_ERR(tl))
> + return PTR_ERR(tl);
> +
> + if (!tl->hwsp_cacheline)
> + goto out_free;
> +
> + for (i = 0; i < ARRAY_SIZE(watcher); i++) {
> + err = setup_watcher(&watcher[i], gt);
> + if (err)
> + goto out;
> + }
> +
> + for_each_engine(engine, gt, id) {
> + struct intel_context *ce;
> + unsigned long count = 0;
> + IGT_TIMEOUT(end_time);
> +
> + /* Create a request we can use for remote reading of the HWSP */
> + err = create_watcher(&watcher[1], engine, SZ_512K);
> + if (err)
> + goto out;
> +
> + do {
> + struct i915_sw_fence *submit;
> + struct i915_request *rq;
> + u32 hwsp;
> +
> + submit = heap_fence_create(GFP_KERNEL);
> + if (!submit) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + err = create_watcher(&watcher[0], engine, SZ_4K);
> + if (err)
> + goto out;
> +
> + ce = intel_context_create(engine);
> + if (IS_ERR(ce)) {
> + err = PTR_ERR(ce);
> + goto out;
> + }
> +
> + /* Skip to the end, saving 30 minutes of nops */
> + tl->seqno = -10u + 2 * (count & 3);
> + WRITE_ONCE(*(u32 *)tl->hwsp_seqno, tl->seqno);
> + ce->timeline = intel_timeline_get(tl);
> +
> + rq = intel_context_create_request(ce);
> + if (IS_ERR(rq)) {
> + err = PTR_ERR(rq);
> + intel_context_put(ce);
> + goto out;
> + }
> +
> + err = i915_sw_fence_await_dma_fence(&rq->submit,
> + &watcher[0].rq->fence, 0,
> + GFP_KERNEL);
> + if (err < 0) {
> + i915_request_add(rq);
> + intel_context_put(ce);
> + goto out;
> + }
> +
> + mutex_lock(&watcher[0].rq->context->timeline->mutex);
> + err = intel_timeline_read_hwsp(rq, watcher[0].rq, &hwsp);
> + if (err == 0)
> + err = emit_read_hwsp(watcher[0].rq, /* before */
> + rq->fence.seqno, hwsp,
> + &watcher[0].addr);
> + mutex_unlock(&watcher[0].rq->context->timeline->mutex);
> + if (err) {
> + i915_request_add(rq);
> + intel_context_put(ce);
> + goto out;
> + }
> +
> + mutex_lock(&watcher[1].rq->context->timeline->mutex);
> + err = intel_timeline_read_hwsp(rq, watcher[1].rq, &hwsp);
> + if (err == 0)
> + err = emit_read_hwsp(watcher[1].rq, /* after */
> + rq->fence.seqno, hwsp,
> + &watcher[1].addr);
> + mutex_unlock(&watcher[1].rq->context->timeline->mutex);
> + if (err) {
> + i915_request_add(rq);
> + intel_context_put(ce);
> + goto out;
> + }
> +
> + i915_request_get(rq);
> + i915_request_add(rq);
> +
> + rq = wrap_timeline(rq);
> + intel_context_put(ce);
> + if (IS_ERR(rq)) {
> + err = PTR_ERR(rq);
> + goto out;
> + }
> +
> + err = i915_sw_fence_await_dma_fence(&watcher[1].rq->submit,
> + &rq->fence, 0,
> + GFP_KERNEL);
> + if (err < 0) {
> + i915_request_put(rq);
> + goto out;
> + }
> +
> + err = check_watcher(&watcher[0], "before", cmp_lt);
> + i915_sw_fence_commit(submit);
> + heap_fence_put(submit);
> + if (err) {
> + i915_request_put(rq);
> + goto out;
> + }
> + count++;
> +
> + if (8 * watcher[1].rq->ring->emit >
> + 3 * watcher[1].rq->ring->size) {
> + i915_request_put(rq);
> + break;
> + }
> +
> + /* Flush the timeline before manually wrapping again */
> + if (i915_request_wait(rq,
> + I915_WAIT_INTERRUPTIBLE,
> + HZ) < 0) {
> + err = -ETIME;
> + i915_request_put(rq);
> + goto out;
> + }
> +
> + retire_requests(tl);
> + i915_request_put(rq);
> + } while (!__igt_timeout(end_time, NULL));
> + WRITE_ONCE(*(u32 *)tl->hwsp_seqno, 0xdeadbeef);
> +
> + pr_info("%s: simulated %lu wraps\n", engine->name, count);
> + err = check_watcher(&watcher[1], "after", cmp_gte);
> + if (err)
> + goto out;
> + }
> +
> +out:
> + for (i = 0; i < ARRAY_SIZE(watcher); i++)
> + cleanup_watcher(&watcher[i]);
> +
> + if (igt_flush_test(gt->i915))
> + err = -EIO;
> +
> +out_free:
> + intel_timeline_put(tl);
> + return err;
> +}
> +
> static int live_hwsp_rollover_kernel(void *arg)
> {
> struct intel_gt *gt = arg;
> @@ -998,6 +1371,7 @@ int intel_timeline_live_selftests(struct drm_i915_private *i915)
> SUBTEST(live_hwsp_engine),
> SUBTEST(live_hwsp_alternate),
> SUBTEST(live_hwsp_wrap),
> + SUBTEST(live_hwsp_read),
> SUBTEST(live_hwsp_rollover_kernel),
> SUBTEST(live_hwsp_rollover_user),
> };
> --
> 2.20.1
>
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