On 11.09.25 16:38, Srinivasan Shanmugam wrote:
> This keeps MMIO_REMAP fixed for its whole lifetime.
> Other buffers (VRAM/GTT) are unchanged.
>
> This change pins it when we export the dma-buf.
> If the export fails, we undo the pin.
> When the dma-buf is released, we unpin it.
>
> MMIO_REMAP (HDP flush page) is a hardware I/O window, not normal RAM.
> It should never be moved
Please pin the MMIO_REMAP BO on creation instead.
It doesn't make any sense to evict that anyway.
Regards,
Christian.
>
> Cc: Christian König <christian.koe...@amd.com>
> Cc: Alex Deucher <alexander.deuc...@amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 36 +++++++++++++++++++--
> 1 file changed, 33 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index f85e16be438f..31d78561ab95 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -47,6 +47,7 @@
> #include <linux/scatterlist.h>
> #include <linux/slab.h>
>
> +static void amdgpu_dmabuf_release(struct dma_buf *dmabuf);
> static const struct dma_buf_attach_ops amdgpu_dma_buf_attach_ops;
>
> /**
> @@ -377,13 +378,27 @@ const struct dma_buf_ops amdgpu_dmabuf_ops = {
> .unpin = amdgpu_dma_buf_unpin,
> .map_dma_buf = amdgpu_dma_buf_map,
> .unmap_dma_buf = amdgpu_dma_buf_unmap,
> - .release = drm_gem_dmabuf_release,
> + .release = amdgpu_dmabuf_release,
> .begin_cpu_access = amdgpu_dma_buf_begin_cpu_access,
> .mmap = drm_gem_dmabuf_mmap,
> .vmap = drm_gem_dmabuf_vmap,
> .vunmap = drm_gem_dmabuf_vunmap,
> };
>
> +/* Drop the export-time pin for MMIO_REMAP when the dma-buf is finally
> released. */
> +static void amdgpu_dmabuf_release(struct dma_buf *dmabuf)
> +{
> + struct drm_gem_object *gobj = dmabuf->priv;
> + struct amdgpu_bo *bo = gem_to_amdgpu_bo(gobj);
> +
> + if (bo && bo->tbo.resource &&
> + bo->tbo.resource->mem_type == AMDGPU_PL_MMIO_REMAP)
> + amdgpu_bo_unpin(bo);
> +
> + drm_gem_dmabuf_release(dmabuf);
> +}
> +
> +
> /**
> * amdgpu_gem_prime_export - &drm_driver.gem_prime_export implementation
> * @gobj: GEM BO
> @@ -399,15 +414,30 @@ struct dma_buf *amdgpu_gem_prime_export(struct
> drm_gem_object *gobj,
> {
> struct amdgpu_bo *bo = gem_to_amdgpu_bo(gobj);
> struct dma_buf *buf;
> + int r;
>
> if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm) ||
> bo->flags & AMDGPU_GEM_CREATE_VM_ALWAYS_VALID)
> return ERR_PTR(-EPERM);
>
> + /* MMIO_REMAP: opt-in + pin at export so later paths never migrate it */
> + if (bo->tbo.resource &&
> + bo->tbo.resource->mem_type == AMDGPU_PL_MMIO_REMAP) {
> + r = amdgpu_bo_pin(bo, AMDGPU_GEM_DOMAIN_GTT);
> + if (r)
> + return ERR_PTR(r);
> + }
> +
> buf = drm_gem_prime_export(gobj, flags);
> - if (!IS_ERR(buf))
> - buf->ops = &amdgpu_dmabuf_ops;
> + if (IS_ERR(buf)) {
> + /* if export failed, drop the pin we took */
> + if (bo->tbo.resource &&
> + bo->tbo.resource->mem_type == AMDGPU_PL_MMIO_REMAP)
> + amdgpu_bo_unpin(bo);
> + return buf;
> + }
>
> + buf->ops = &amdgpu_dmabuf_ops;
> return buf;
> }
>
