Add support for the USE_USERPTR blob flag in virtio-gpu to enable
user pointer mapping for blob resources. This allows guest applications
to use user-allocated memory for GPU resources more efficiently.

Changes include:
- Add VIRTIO_GPU_BLOB_FLAG_USE_USERPTR flag definition
- Enhance blob resource creation to handle userptr flag properly
- Remove arbitrary nr_entries limit (16384) in mapping creation
- Add conditional handling for userptr vs regular blob mapping
- Support guest_blob_mapped parameter for virgl renderer
- Fix value check issue in virtio-gpu

This enables more flexible memory management between guest and host
for GPU virtualization scenarios.

Signed-off-by: Honglei Huang <honghuan@amd.com>
---
 hw/display/virtio-gpu.c                     | 7 -------
 include/standard-headers/linux/virtio_gpu.h | 1 +
 2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index 643e91ca2a..17df148920 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -808,13 +808,6 @@ int virtio_gpu_create_mapping_iov(VirtIOGPU *g,
     size_t esize, s;
     int e, v;
 
-    if (nr_entries > 16384) {
-        qemu_log_mask(LOG_GUEST_ERROR,
-                      "%s: nr_entries is too big (%d > 16384)\n",
-                      __func__, nr_entries);
-        return -1;
-    }
-
     esize = sizeof(*ents) * nr_entries;
     ents = g_malloc(esize);
     s = iov_to_buf(cmd->elem.out_sg, cmd->elem.out_num,
diff --git a/include/standard-headers/linux/virtio_gpu.h b/include/standard-headers/linux/virtio_gpu.h
index 00cd3f04af..b85e781a2d 100644
--- a/include/standard-headers/linux/virtio_gpu.h
+++ b/include/standard-headers/linux/virtio_gpu.h
@@ -405,6 +405,7 @@ struct virtio_gpu_resource_create_blob {
 #define VIRTIO_GPU_BLOB_FLAG_USE_MAPPABLE     0x0001
 #define VIRTIO_GPU_BLOB_FLAG_USE_SHAREABLE    0x0002
 #define VIRTIO_GPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
+#define VIRTIO_GPU_BLOB_FLAG_USE_USERPTR      0x0008
 	/* zero is invalid blob mem */
 	uint32_t blob_mem;
 	uint32_t blob_flags;
-- 
2.34.1

On Wed, Jan 07 2026, Honglei Huang <honghuan@amd.com> wrote:

> Add support for the USE_USERPTR blob flag in virtio-gpu to enable
> user pointer mapping for blob resources. This allows guest applications
> to use user-allocated memory for GPU resources more efficiently.
>
> Changes include:
> - Add VIRTIO_GPU_BLOB_FLAG_USE_USERPTR flag definition
> - Enhance blob resource creation to handle userptr flag properly
> - Remove arbitrary nr_entries limit (16384) in mapping creation
> - Add conditional handling for userptr vs regular blob mapping
> - Support guest_blob_mapped parameter for virgl renderer
> - Fix value check issue in virtio-gpu
>
> This enables more flexible memory management between guest and host
> for GPU virtualization scenarios.
>
> Signed-off-by: Honglei Huang <honghuan@amd.com>
> ---
>  hw/display/virtio-gpu.c                     | 7 -------
>  include/standard-headers/linux/virtio_gpu.h | 1 +
>  2 files changed, 1 insertion(+), 7 deletions(-)

Please split out any updates to the imported Linux headers into a
separate patch to be replaced by a headers sync (I thought checkpatch
would warn about that?)

On 2026/1/7 17:42, Cornelia Huck wrote:
> On Wed, Jan 07 2026, Honglei Huang <honghuan@amd.com> wrote:
> 
>> Add support for the USE_USERPTR blob flag in virtio-gpu to enable
>> user pointer mapping for blob resources. This allows guest applications
>> to use user-allocated memory for GPU resources more efficiently.
>>
>> Changes include:
>> - Add VIRTIO_GPU_BLOB_FLAG_USE_USERPTR flag definition
>> - Enhance blob resource creation to handle userptr flag properly
>> - Remove arbitrary nr_entries limit (16384) in mapping creation
>> - Add conditional handling for userptr vs regular blob mapping
>> - Support guest_blob_mapped parameter for virgl renderer
>> - Fix value check issue in virtio-gpu
>>
>> This enables more flexible memory management between guest and host
>> for GPU virtualization scenarios.
>>
>> Signed-off-by: Honglei Huang <honghuan@amd.com>
>> ---
>>   hw/display/virtio-gpu.c                     | 7 -------
>>   include/standard-headers/linux/virtio_gpu.h | 1 +
>>   2 files changed, 1 insertion(+), 7 deletions(-)
> 
> Please split out any updates to the imported Linux headers into a
> separate patch to be replaced by a headers sync (I thought checkpatch
> would warn about that?)
> 

Understood, will split the Linux headrs changes into a separate commit 
in next version.
Really thanks for the reminding.

Regards,
Honglei