On 2026/02/28 7:13, Vivek Kasireddy wrote:
In addition to memfd, a blob resource can also have its backing
storage in a VFIO device region. Since, there is no effective way
to determine where the backing storage is located, we first try to
create a dmabuf assuming it is in memfd. If that fails, we try to
create a dmabuf assuming it is in VFIO device region.
So, we first call virtio_gpu_create_udmabuf() to check if the blob's
backing storage is located in a memfd or not. If it is not, we invoke
the vfio_device_create_dmabuf_fd() API which identifies the right
VFIO device and eventually creates a dmabuf fd.
Note that in virtio_gpu_remap_dmabuf(), we first try to test if
the VFIO dmabuf exporter supports mmap or not. If it doesn't, we
fall back to the vfio_device_mmap_dmabuf() API to get a mapping
created for the dmabuf.
Cc: Marc-André Lureau <[email protected]>
Cc: Alex Bennée <[email protected]>
Cc: Akihiko Odaki <[email protected]>
Cc: Dmitry Osipenko <[email protected]>
Cc: Alex Williamson <[email protected]>
Cc: Cédric Le Goater <[email protected]>
Signed-off-by: Vivek Kasireddy <[email protected]>
---
hw/display/virtio-gpu-dmabuf.c | 35 +++++++++++++++++++++++++++-------
1 file changed, 28 insertions(+), 7 deletions(-)
diff --git a/hw/display/virtio-gpu-dmabuf.c b/hw/display/virtio-gpu-dmabuf.c
index b2badfc1bd..533d3d601c 100644
--- a/hw/display/virtio-gpu-dmabuf.c
+++ b/hw/display/virtio-gpu-dmabuf.c
@@ -74,13 +74,21 @@ static int virtio_gpu_create_udmabuf(struct
virtio_gpu_simple_resource *res,
static bool virtio_gpu_remap_dmabuf(struct virtio_gpu_simple_resource *res,
Error **errp)
{
+ Error *mmap_err = NULL;
void *map;
map = mmap(NULL, res->blob_size, PROT_READ, MAP_SHARED, res->dmabuf_fd, 0);
if (map == MAP_FAILED) {
- error_setg_errno(errp, errno, "dmabuf mmap failed");
+ error_setg_errno(&mmap_err, errno, "dmabuf mmap failed: ");
res->remapped = NULL;
- return false;
+
+ if (!vfio_device_mmap_dmabuf(res->iov, res->iov_cnt, &map,
+ res->blob_size, errp)) {
Let's call vfio_device_mmap_dmabuf() only when
vfio_device_create_dmabuf_fd() is called. Hopefully it will simplify the
logic structure.
Regards,
Akihiko Odaki
+ error_report_err(mmap_err);
+ return false;
+ }
+ error_free(mmap_err);
+ mmap_err = NULL;
}
res->remapped = map;
return true;
@@ -137,7 +145,7 @@ bool virtio_gpu_have_udmabuf(void)
void virtio_gpu_init_dmabuf(struct virtio_gpu_simple_resource *res)
{
- Error *local_err = NULL;
+ Error *local_err = NULL, *vfio_err = NULL;
void *pdata = NULL;
int ret;
@@ -151,15 +159,28 @@ void virtio_gpu_init_dmabuf(struct virtio_gpu_simple_resource *res)
error_prepend(&local_err, "Cannot create dmabuf: ");
if (ret == VFIO_DMABUF_CREATE_GUEST_ERROR) {
- qemu_log_mask(LOG_GUEST_ERROR,
- "Cannot create dmabuf: incompatible memory\n");
- error_free(local_err);
- return;
+ ret = vfio_device_create_dmabuf_fd(res->iov, res->iov_cnt,
+ &vfio_err);
+ if (ret > 0) {
+ error_free(local_err);
+ local_err = NULL;
+ goto out;
+ }
+
+ if (ret == VFIO_DMABUF_CREATE_GUEST_ERROR) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "Cannot create dmabuf: incompatible
memory\n");
+ error_free(vfio_err);
+ error_free(local_err);
+ return;
+ }
+ error_report_err(vfio_err);
}
error_report_err(local_err);
return;
}
+out:
res->dmabuf_fd = ret;
if (!virtio_gpu_remap_dmabuf(res, &local_err)) {
error_report_err(local_err);
