linux-kernel - Re: [PATCH v2 0/7] *** Add virtio gpu userptr support ***

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Message-ID: <3baabd6b-95ba-4f84-bdef-b44d6d071aba@gmail.com>
Date: Sat, 29 Mar 2025 15:56:00 -0400
From: Demi Marie Obenour <demiobenour@...il.com>
To: Honglei Huang <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, Dmitry Osipenko <dmitry.osipenko@...labora.com>
Subject: Re: [PATCH v2 0/7] *** Add virtio gpu userptr support ***

On 3/21/25 4:00 AM, Honglei Huang wrote:
> From: Honglei Huang <Honglei1.Huang@....com>
> 
> Hello,
> 
> This series add virtio gpu userptr support and add libhsakmt capset.
> The userptr feature is used for let host access guest user space memory,
> this feature is used for GPU compute use case, to enable ROCm/OpenCL native
> context. It should be pointed out that we are not to implement SVM here, 
> this is just a buffer based userptr implementation.
> The libhsakmt capset is used for ROCm context, libhsakmt is like the role 
> of libdrm in Mesa.
> 
> Patches 1-2 add libhsakmt capset and userptr blob resource flag.

libhsakmt and userptr are orthogonal from each other.
Should the libhsakmt context be a separate patch series?

> Patches 3-5 implement basic userptr feature, in some popular bench marks,
> it has an efficiency of about 70% compared to bare metal in OpenCL API.
> Patch 6 adds interval tree to manage userptrs and prevent duplicate creation.
> 
> V2: - Split add HSAKMT context and blob userptr resource to two patches.
>     - Remove MMU notifier related patches, cause use not moveable user space
>       memory with MMU notifier is not a good idea.
>     - Remove HSAKMT context check when create context, let all the context
>       support the userptr feature.
>     - Remove MMU notifier related content in cover letter.
>     - Add more comments  for patch 6 in cover letter.

I have not looked at the implementation, but thanks for removing the MMU
notifier support.  Should the interval tree be added before the feature
is exposed to userspace?  That would prevent users who are doing kernel
bisects from temporarily exposing a buggy feature to userspace.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)