[PATCH v1 1/2] drm/i915/gem: Correct the locking and pin pattern for dma-buf
Michael J. Ruhl
michael.j.ruhl at intel.com
Thu Jul 1 20:20:13 UTC 2021
From: Thomas Hellström <thomas.hellstrom at linux.intel.com>
If our exported dma-bufs are imported by another instance of our driver,
that instance will typically have the imported dma-bufs locked during
dma_buf_map_attachment(). But the exporter also locks the same reservation
object in the map_dma_buf() callback, which leads to recursive locking.
So taking the lock inside _pin_pages_unlocked() is incorrect.
Additionally, the current pinning code path is contrary to the defined
way that pinning should occur.
Remove the explicit pin/unpin from the map/umap functions and move them
to the attach/detach allowing correct locking to occur, and to match
the static dma-buf drm_prime pattern.
Add a live selftest to exercise both dynamic and non-dynamic
exports.
v2:
- Extend the selftest with a fake dynamic importer.
- Provide real pin and unpin callbacks to not abuse the interface.
v3: (ruhl)
- Remove the dynamic export support and move the pinning into the
attach/detach path.
v4: (ruhl)
- Put pages does not need to assert on the dma-resv
Reported-by: Michael J. Ruhl <michael.j.ruhl at intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl at intel.com>
---
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 44 +++++--
.../drm/i915/gem/selftests/i915_gem_dmabuf.c | 116 +++++++++++++++++-
2 files changed, 146 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index 616c3a2f1baf..ccae17d5f441 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -12,6 +12,8 @@
#include "i915_gem_object.h"
#include "i915_scatterlist.h"
+I915_SELFTEST_DECLARE(static bool force_different_devices;)
+
static struct drm_i915_gem_object *dma_buf_to_obj(struct dma_buf *buf)
{
return to_intel_bo(buf->priv);
@@ -25,15 +27,11 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attachme
struct scatterlist *src, *dst;
int ret, i;
- ret = i915_gem_object_pin_pages_unlocked(obj);
- if (ret)
- goto err;
-
/* Copy sg so that we make an independent mapping */
st = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
if (st == NULL) {
ret = -ENOMEM;
- goto err_unpin_pages;
+ goto err;
}
ret = sg_alloc_table(st, obj->mm.pages->nents, GFP_KERNEL);
@@ -58,8 +56,6 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attachme
sg_free_table(st);
err_free:
kfree(st);
-err_unpin_pages:
- i915_gem_object_unpin_pages(obj);
err:
return ERR_PTR(ret);
}
@@ -68,13 +64,9 @@ static void i915_gem_unmap_dma_buf(struct dma_buf_attachment *attachment,
struct sg_table *sg,
enum dma_data_direction dir)
{
- struct drm_i915_gem_object *obj = dma_buf_to_obj(attachment->dmabuf);
-
dma_unmap_sgtable(attachment->dev, sg, dir, DMA_ATTR_SKIP_CPU_SYNC);
sg_free_table(sg);
kfree(sg);
-
- i915_gem_object_unpin_pages(obj);
}
static int i915_gem_dmabuf_vmap(struct dma_buf *dma_buf, struct dma_buf_map *map)
@@ -168,7 +160,32 @@ static int i915_gem_end_cpu_access(struct dma_buf *dma_buf, enum dma_data_direct
return err;
}
+/**
+ * i915_gem_dmabuf_attach - Do any extra attach work necessary
+ * @dmabuf: imported dma-buf
+ * @attach: new attach to do work on
+ *
+ */
+static int i915_gem_dmabuf_attach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *attach)
+{
+ struct drm_i915_gem_object *obj = dma_buf_to_obj(dmabuf);
+
+ assert_object_held(obj);
+ return i915_gem_object_pin_pages(obj);
+}
+
+static void i915_gem_dmabuf_detach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *attach)
+{
+ struct drm_i915_gem_object *obj = dma_buf_to_obj(dmabuf);
+
+ i915_gem_object_unpin_pages(obj);
+}
+
static const struct dma_buf_ops i915_dmabuf_ops = {
+ .attach = i915_gem_dmabuf_attach,
+ .detach = i915_gem_dmabuf_detach,
.map_dma_buf = i915_gem_map_dma_buf,
.unmap_dma_buf = i915_gem_unmap_dma_buf,
.release = drm_gem_dmabuf_release,
@@ -204,6 +221,8 @@ static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj)
struct sg_table *pages;
unsigned int sg_page_sizes;
+ assert_object_held(obj);
+
pages = dma_buf_map_attachment(obj->base.import_attach,
DMA_BIDIRECTIONAL);
if (IS_ERR(pages))
@@ -241,7 +260,8 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
if (dma_buf->ops == &i915_dmabuf_ops) {
obj = dma_buf_to_obj(dma_buf);
/* is it from our device? */
- if (obj->base.dev == dev) {
+ if (obj->base.dev == dev &&
+ !I915_SELFTEST_ONLY(force_different_devices)) {
/*
* Importing dmabuf exported from out own gem increases
* refcount on gem itself instead of f_count of dmabuf.
diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
index dd74bc09ec88..868b3469ecbd 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
@@ -35,7 +35,7 @@ static int igt_dmabuf_export(void *arg)
static int igt_dmabuf_import_self(void *arg)
{
struct drm_i915_private *i915 = arg;
- struct drm_i915_gem_object *obj;
+ struct drm_i915_gem_object *obj, *import_obj;
struct drm_gem_object *import;
struct dma_buf *dmabuf;
int err;
@@ -65,14 +65,125 @@ static int igt_dmabuf_import_self(void *arg)
err = -EINVAL;
goto out_import;
}
+ import_obj = to_intel_bo(import);
+
+ i915_gem_object_lock(import_obj, NULL);
+ err = ____i915_gem_object_get_pages(import_obj);
+ i915_gem_object_unlock(import_obj);
+ if (err) {
+ pr_err("Same object dma-buf get_pages failed!\n");
+ goto out_import;
+ }
err = 0;
out_import:
- i915_gem_object_put(to_intel_bo(import));
+ i915_gem_object_put(import_obj);
+out_dmabuf:
+ dma_buf_put(dmabuf);
+out:
+ i915_gem_object_put(obj);
+ return err;
+}
+
+static void igt_dmabuf_move_notify(struct dma_buf_attachment *attach)
+{
+ GEM_WARN_ON(1);
+}
+
+static const struct dma_buf_attach_ops igt_dmabuf_attach_ops = {
+ .move_notify = igt_dmabuf_move_notify,
+};
+
+static int igt_dmabuf_import_same_driver(void *arg)
+{
+ struct drm_i915_private *i915 = arg;
+ struct drm_i915_gem_object *obj, *import_obj;
+ struct drm_gem_object *import;
+ struct dma_buf *dmabuf;
+ struct dma_buf_attachment *import_attach;
+ struct sg_table *st;
+ long timeout;
+ int err;
+
+ force_different_devices = true;
+ obj = i915_gem_object_create_shmem(i915, PAGE_SIZE);
+ if (IS_ERR(obj))
+ goto out_ret;
+
+ dmabuf = i915_gem_prime_export(&obj->base, 0);
+ if (IS_ERR(dmabuf)) {
+ pr_err("i915_gem_prime_export failed with err=%d\n",
+ (int)PTR_ERR(dmabuf));
+ err = PTR_ERR(dmabuf);
+ goto out;
+ }
+
+ import = i915_gem_prime_import(&i915->drm, dmabuf);
+ if (IS_ERR(import)) {
+ pr_err("i915_gem_prime_import failed with err=%d\n",
+ (int)PTR_ERR(import));
+ err = PTR_ERR(import);
+ goto out_dmabuf;
+ }
+
+ if (import == &obj->base) {
+ pr_err("i915_gem_prime_import reused gem object!\n");
+ err = -EINVAL;
+ goto out_import;
+ }
+
+ import_obj = to_intel_bo(import);
+
+ i915_gem_object_lock(import_obj, NULL);
+ err = ____i915_gem_object_get_pages(import_obj);
+ if (err) {
+ pr_err("Different objects dma-buf get_pages failed!\n");
+ i915_gem_object_unlock(import_obj);
+ goto out_import;
+ }
+
+ /*
+ * If the exported object is not in system memory, something
+ * weird is going on. TODO: When p2p is supported, this is no
+ * longer considered weird.
+ */
+ if (obj->mm.region != i915->mm.regions[INTEL_REGION_SMEM]) {
+ pr_err("Exported dma-buf is not in system memory\n");
+ err = -EINVAL;
+ }
+
+ i915_gem_object_unlock(import_obj);
+
+ /* Now try a fake dynamic importer */
+ import_attach = dma_buf_dynamic_attach(dmabuf, obj->base.dev->dev,
+ &igt_dmabuf_attach_ops,
+ NULL);
+ if (IS_ERR(import_attach))
+ goto out_import;
+
+ dma_resv_lock(dmabuf->resv, NULL);
+ st = dma_buf_map_attachment(import_attach, DMA_BIDIRECTIONAL);
+ dma_resv_unlock(dmabuf->resv);
+ if (IS_ERR(st))
+ goto out_detach;
+
+ timeout = dma_resv_wait_timeout(dmabuf->resv, false, true, 5 * HZ);
+ if (!timeout) {
+ pr_err("dmabuf wait for exclusive fence timed out.\n");
+ timeout = -ETIME;
+ }
+ err = timeout > 0 ? 0 : timeout;
+ dma_buf_unmap_attachment(import_attach, st, DMA_BIDIRECTIONAL);
+out_detach:
+ dma_buf_detach(dmabuf, import_attach);
+out_import:
+ i915_gem_object_put(import_obj);
out_dmabuf:
dma_buf_put(dmabuf);
out:
i915_gem_object_put(obj);
+out_ret:
+ force_different_devices = false;
return err;
}
@@ -286,6 +397,7 @@ int i915_gem_dmabuf_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
SUBTEST(igt_dmabuf_export),
+ SUBTEST(igt_dmabuf_import_same_driver),
};
return i915_subtests(tests, i915);
--
2.31.1
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