On Thu, Mar 6, 2025 at 2:52 AM Huang, Honglei1 <Honglei1.Huang@xxxxxxx> 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@xxxxxxx>
>>
>> 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.
I wonder if you can emulate userptr using udmabuf on the host-side?
Essentially for the guest, it'll be a malloc'ed memory, which means a guest sg list. We can convert the guest sg-list to udmabuf using well-known mechanisms on the host side. I hope amdkfd can operate on dma-bufs too?
I do such a feature that would have a more generic utility outside of HSAKMT contexts and not rely on Xen-specific grant tables ... checkout VIRTIO_GPU_BLOB_FLAG_CREATE_GUEST_HANDLE in crosvm for an example.
Regards,
Honglei
