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Date: Fri, 19 Dec 2025 13:25:05 +0100
Message-Id: <DF26WBIDPMPU.3E6XTUPMZTHW1@kernel.org>
To: "Alice Ryhl" <aliceryhl@google.com>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH 2/4] drm/gpuvm: drm_gpuvm_bo_obtain() requires lock and
 staged mode
Cc: "Daniel Almeida" <daniel.almeida@collabora.com>, "Matthew Brost"
 <matthew.brost@intel.com>, =?utf-8?q?Thomas_Hellstr=C3=B6m?=
 <thomas.hellstrom@linux.intel.com>, "Maarten Lankhorst"
 <maarten.lankhorst@linux.intel.com>, "Maxime Ripard" <mripard@kernel.org>,
 "Thomas Zimmermann" <tzimmermann@suse.de>, "David Airlie"
 <airlied@gmail.com>, "Simona Vetter" <simona@ffwll.ch>, "Boris Brezillon"
 <boris.brezillon@collabora.com>, "Steven Price" <steven.price@arm.com>,
 "Liviu Dudau" <liviu.dudau@arm.com>, "Miguel Ojeda" <ojeda@kernel.org>,
 "Boqun Feng" <boqun.feng@gmail.com>, "Gary Guo" <gary@garyguo.net>,
 =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, "Benno Lossin"
 <lossin@kernel.org>, "Andreas Hindborg" <a.hindborg@kernel.org>, "Trevor
 Gross" <tmgross@umich.edu>, "Frank Binns" <frank.binns@imgtec.com>, "Matt
 Coster" <matt.coster@imgtec.com>, "Rob Clark"
 <robin.clark@oss.qualcomm.com>, "Dmitry Baryshkov" <lumag@kernel.org>,
 "Abhinav Kumar" <abhinav.kumar@linux.dev>, "Jessica Zhang"
 <jessica.zhang@oss.qualcomm.com>, "Sean Paul" <sean@poorly.run>, "Marijn
 Suijten" <marijn.suijten@somainline.org>, "Lyude Paul" <lyude@redhat.com>,
 "Lucas De Marchi" <lucas.demarchi@intel.com>, "Rodrigo Vivi"
 <rodrigo.vivi@intel.com>, "Sumit Semwal" <sumit.semwal@linaro.org>,
 =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
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References: <20251128-gpuvm-rust-v1-0-ebf66bf234e0@google.com>
 <20251128-gpuvm-rust-v1-2-ebf66bf234e0@google.com>
In-Reply-To: <20251128-gpuvm-rust-v1-2-ebf66bf234e0@google.com>

On Fri Nov 28, 2025 at 3:14 PM CET, Alice Ryhl wrote:
> In the previous commit we updated drm_gpuvm_bo_obtain_prealloc() to take
> locks internally, which means that it's only usable in immediate mode.
> In this commit, we notice that drm_gpuvm_bo_obtain() requires you to use
> staged mode. This means that we now have one variant of obtain for each
> mode you might use gpuvm in.
>
> To reflect this information, we add a warning about using it in
> immediate mode, and to make the distinction clearer we rename the method
> with a _locked() suffix so that it's clear that it requires the caller
> to take the locks.
>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>

Ultimately, the two different approaches of obtaining a VM_BO have always b=
een
desinged for the two different modes of operation -- great to see this refi=
ned!

Given that, I think it would be great to update the "Locking" section of th=
e
GPUVM's documentation and expand it with a new section "Modes of Operation"=
.

Mind sending a follow-up patch / series for this?