On 2025/09/13 11:48, Kasireddy, Vivek wrote:
Hi Akihiko,
Subject: Re: [RFC 4/6] virtio-gpu: Don't rely on res->blob to identify blob
resources
On 2025/09/03 7:42, Vivek Kasireddy wrote:
The res->blob pointer is only valid for blobs that have their
backing storage in memfd. Therefore, we cannot use it to determine
if a resource is a blob or not. Instead, we could use res->blob_size
to make this determination as it is non-zero for blob resources
regardless of where their backing storage is located.
I guess this change needs to be applied before "[RFC 3/6]
virtio-gpu-udmabuf: Create dmabuf for blobs associated with VFIO
devices"; without this patch, the "create dmabuf" patch will probably
create an invalid blob.
Ok, makes sense. I'll move it earlier in the patch series.
Cc: Marc-André Lureau <[email protected]>
Cc: Alex Bennée <[email protected]>
Cc: Akihiko Odaki <[email protected]>
Cc: Dmitry Osipenko <[email protected]>
Signed-off-by: Vivek Kasireddy <[email protected]>
---
hw/display/virtio-gpu.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index 0a1a625b0e..2f9133c3b6 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -57,7 +57,7 @@ void virtio_gpu_update_cursor_data(VirtIOGPU *g,
}
if (res->blob_size) {
- if (res->blob_size < (s->current_cursor->width *
+ if (!res->blob || res->blob_size < (s->current_cursor->width *
I doubt that rejecting a valid blob due to an implementation concern
(whether the backing storage is in memfd) is tolerated in the specification.
Are you suggesting that the whole if (res->blob_size <
(s->current_cursor->width *...
check needs to be removed? I think it is just a sanity check to ensure that the
blob
size is big enough for cursor.
I referred to !res->blob, the new condition. It rejects a valid blob
that is backed by VFIO.
Regards,
Akihiko Odaki
