Re: [PATCH v1 1/7] virtio-gpu api: add blob userptr resource

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

On 3/6/25 13:51, Huang, Honglei1 wrote:
> 
> On 2025/3/1 5:21, Demi Marie Obenour wrote:
>> On 2/28/25 12:36 AM, Honglei Huang wrote:
>>> From: Honglei Huang <Honglei1.Huang@amd.com>
>>>
>>> Add a new resource for blob resource, called userptr, used for let
>>> host access guest user space memory, to acquire buffer based userptr
>>> feature in virtio GPU.
>>>
>>> - The capset VIRTIO_GPU_CAPSET_HSAKMT used for context init,
>>> in this series patches only HSAKMT context can use the userptr
>>> feature. HSAKMT is a GPU compute library in HSA stack, like
>>> the role libdrm in mesa stack.
>>
>> Userptr should not be limited to HSMKMT contexts.  Userptr can
>> accelerate shm buffers by avoiding a copy from guest to host, and
>> it can be implemented using grant tables on Xen.
> 
> Yes, I totally agree userptr can accelerate shm buffers, but I currently
> don't know if there are any other projects working on similar features,
> or if maintainers have any opinions or better ways to implement them, so
> I temporarily limit this feature to HSAKMT context only.
> 
> I am waiting for everyone's opinions, please provide your thoughts.

USERPTR should be relevant for anything Vulkan-related, like Venus and
native contexts. I expect that this new feature will work universally
good for all context types.

In order to merge USERPTR support upstream, we at least will need to
prototype the guest USERPTR in one of native context driver to know that
it works. You'll need to post the whole set of host/guest USERPTR
patches including QEMU and etc, not just the kernel patches.

-- 
Best regards,
Dmitry