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drm/virtio: Support partial maps of GEM objects

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Those are useful to implement coherent cross-vm mmap.

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250109-virtgpu-gem-partial-map-v1-1-a914b48776bd@gmail.com
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
[dmitry.osipenko@collabora.com: Corrected vm_size check to account vm_pgoff]
This commit is contained in:
Sasha Finkelstein 2025-01-09 22:45:46 +01:00 • committed by Dmitry Osipenko
parent 3ab334814d
commit 7f3b11934f
1 changed files with 6 additions and 3 deletions
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9
drivers/gpu/drm/virtio/virtgpu_vram.c
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@ -37,6 +37,7 @@ static int virtio_gpu_vram_mmap(struct drm_gem_object *obj,
struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
struct virtio_gpu_object_vram *vram = to_virtio_gpu_vram(bo);
unsigned long vm_size = vma->vm_end - vma->vm_start;
unsigned long vm_end;
if (!(bo->blob_flags & VIRTGPU_BLOB_FLAG_USE_MAPPABLE))
return -EINVAL;
@ -56,12 +57,14 @@ static int virtio_gpu_vram_mmap(struct drm_gem_object *obj,
else if (vram->map_info == VIRTIO_GPU_MAP_CACHE_UNCACHED)
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
/* Partial mappings of GEM buffers don't happen much in practice. */
if (vm_size != vram->vram_node.size)
if (check_add_overflow(vma->vm_pgoff << PAGE_SHIFT, vm_size, &vm_end))
return -EINVAL;
if (vm_end > vram->vram_node.size)
return -EINVAL;
ret = io_remap_pfn_range(vma, vma->vm_start,
vram->vram_node.start >> PAGE_SHIFT,
(vram->vram_node.start >> PAGE_SHIFT) + vma->vm_pgoff,
vm_size, vma->vm_page_prot);
return ret;
}