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

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Message-ID: <42048a80-a736-4ccc-953b-924d1e640cd0@gmail.com>
Date: Sat, 29 Mar 2025 15:50:46 -0400
From: Demi Marie Obenour <demiobenour@...il.com>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>,
 "Huang, Honglei1" <Honglei1.Huang@....com>, David Airlie
 <airlied@...hat.com>, Gerd Hoffmann <kraxel@...hat.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Simona Vetter <simona@...ll.ch>, Rob Clark <robdclark@...il.com>,
 Huang Rui <ray.huang@....com>
Cc: dri-devel@...ts.freedesktop.org, virtualization@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/7] virtio-gpu api: add blob userptr resource

On 3/26/25 10:46 AM, 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@....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.

Does the user-mode VMM need to be QEMU or would patches to
another open-source VMM, such as crosvm, be sufficient?
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)