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drm/i915/gem: Correct the locking and pin pattern for dma-buf (v8) 

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
v5: (jason)
- Lock around dma_buf_unmap_attachment() when emulating a dynamic
  importer in the subtests.
- Use pin_pages_unlocked
v6: (jason)
- Use dma_buf_attach instead of dma_buf_attach_dynamic in the selftests
v7: (mauld)
- Use __i915_gem_object_get_pages (2 __underscores) instead of the
  4 ____underscore version in the selftests
v8: (mauld)
- Drop the kernel doc from the static i915_gem_dmabuf_attach function
- Add missing "err = PTR_ERR()" to a bunch of selftest error cases

Reported-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723172142.3273510-8-jason@jlekstrand.net
This commit is contained in:
Thomas Hellström 2021-07-23 12:21:41 -05:00 committed by Matthew Auld
parent 76b62448dc
commit d7b2cb380b
2 changed files with 132 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
View File

@ -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 @@ err_free_sg:
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 +160,25 @@ retry:
return err;
}
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);
return i915_gem_object_pin_pages_unlocked(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 +214,8 @@ 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 +253,8 @@ 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.

109
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
View File

@ -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;
@ -65,10 +65,19 @@ 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:
@ -76,6 +85,101 @@ out:
return err;
}
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)) {
err = PTR_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=%ld\n",
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=%ld\n",
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 an importer */
import_attach = dma_buf_attach(dmabuf, obj->base.dev->dev);
if (IS_ERR(import_attach)) {
err = PTR_ERR(import_attach);
goto out_import;
}
st = dma_buf_map_attachment(import_attach, DMA_BIDIRECTIONAL);
if (IS_ERR(st)) {
err = PTR_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;
}
static int igt_dmabuf_import(void *arg)
{
struct drm_i915_private *i915 = arg;
@ -286,6 +390,7 @@ 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);