On Fri, 16 Jul 2021 at 15:14, Jason Ekstrand jason@jlekstrand.net wrote:
From: Thomas Hellström thomas.hellstrom@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
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
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
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 43 ++++++-- .../drm/i915/gem/selftests/i915_gem_dmabuf.c | 103 +++++++++++++++++- 2 files changed, 132 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 616c3a2f1baf0..9a655f69a0671 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 +160,31 @@ 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);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);+}
We don't normally add kernel-doc for static functions? Otherwise dmabuf_detach() needs matching kernel-doc.
<snip>
+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)
<snip>
/* Now try a fake an importer */import_attach = dma_buf_attach(dmabuf, obj->base.dev->dev);if (IS_ERR(import_attach))goto out_import;st = dma_buf_map_attachment(import_attach, DMA_BIDIRECTIONAL);if (IS_ERR(st))goto out_detach;
For these two maybe missing err = ?