The is_vram() is checking the current placement, however if we consider exported VRAM with dynamic dma-buf, it looks possible for the xe driver to async evict the memory, notifying the importer, however importer does not have to call unmap_attachment() immediately, but rather just as "soon as possible", like when the dma-resv idles. Following from this we would then pipeline the move, attaching the fence to the manager, and then update the current placement. But when the unmap_attachment() runs at some later point we might see that is_vram() is now false, and take the complete wrong path when dma-unmapping the sg, leading to explosions.
To fix this rather make a note in the attachment if the sg was originally mapping vram or tt pages.
Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4563 Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs") Signed-off-by: Matthew Auld matthew.auld@intel.com Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Cc: Matthew Brost matthew.brost@intel.com Cc: stable@vger.kernel.org # v6.8+ --- drivers/gpu/drm/xe/xe_dma_buf.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c index f67803e15a0e..b71058e26820 100644 --- a/drivers/gpu/drm/xe/xe_dma_buf.c +++ b/drivers/gpu/drm/xe/xe_dma_buf.c @@ -22,6 +22,22 @@
MODULE_IMPORT_NS("DMA_BUF");
+/** + * struct xe_sg_info - Track the exported sg info + */ +struct xe_sg_info { + /** @is_vram: True if this sg is mapping VRAM. */ + bool is_vram; +}; + +static struct xe_sg_info tt_sg_info = { + .is_vram = false, +}; + +static struct xe_sg_info vram_sg_info = { + .is_vram = true, +}; + static int xe_dma_buf_attach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach) { @@ -118,6 +134,7 @@ static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach, if (dma_map_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC)) goto error_free; + attach->priv = &tt_sg_info; break;
case XE_PL_VRAM0: @@ -128,6 +145,7 @@ static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach, dir, &sgt); if (r) return ERR_PTR(r); + attach->priv = &vram_sg_info; break; default: return ERR_PTR(-EINVAL); @@ -145,10 +163,9 @@ static void xe_dma_buf_unmap(struct dma_buf_attachment *attach, struct sg_table *sgt, enum dma_data_direction dir) { - struct dma_buf *dma_buf = attach->dmabuf; - struct xe_bo *bo = gem_to_xe_bo(dma_buf->priv); + struct xe_sg_info *sg_info = attach->priv;
- if (!xe_bo_is_vram(bo)) { + if (!sg_info->is_vram) { dma_unmap_sgtable(attach->dev, sgt, dir, 0); sg_free_table(sgt); kfree(sgt);