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

From: Huang, Honglei1
Date: Wed Mar 26 2025 - 23:00:53 EST




On 2025/3/26 22:46, Dmitry Osipenko wrote:
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@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.

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.

Ok totally understood, I will upload other components as soon as possiable, cause we only have limited resource for this matter, please understand the speed is relatively slow.
And for Vulkan use case, yes it is very important, I will make some prototype implementation for it, and will test it locally. The implementation for USERPTR must comply with Vulakan's standard.
Really thanks for your comments.

Reagrds,
Honglei