linux-kernel - Re: [PATCH drm-next v6 02/13] drm: manager to keep track of GPUs VA mappings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230630114045.20743fab@collabora.com>
Date:   Fri, 30 Jun 2023 11:40:45 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Danilo Krummrich <dakr@...hat.com>
Cc:     airlied@...il.com, daniel@...ll.ch, tzimmermann@...e.de,
        mripard@...nel.org, corbet@....net, christian.koenig@....com,
        bskeggs@...hat.com, Liam.Howlett@...cle.com,
        matthew.brost@...el.com, alexdeucher@...il.com, ogabbay@...nel.org,
        bagasdotme@...il.com, willy@...radead.org, jason@...kstrand.net,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Donald Robson <donald.robson@...tec.com>,
        Dave Airlie <airlied@...hat.com>
Subject: Re: [PATCH drm-next v6 02/13] drm: manager to keep track of GPUs VA
 mappings

On Fri, 30 Jun 2023 10:02:52 +0200
Boris Brezillon <boris.brezillon@...labora.com> wrote:

> In practice, I don't expect things to deadlock, because the VM resv is
> not supposed to be taken outside the VM context and the locking order
> is always the same (VM lock first, and then each shared BO
> taken/released independently), but I'm not super thrilled by this
> nested lock, and I'm wondering if we shouldn't have a pass collecting
> locks in a drm_exec context first, and then have
> the operations executed. IOW, something like that:
> 
> 	drm_exec_init(exec, DRM_EXEC_IGNORE_DUPLICATES)
> 	drm_exec_until_all_locked(exec) {
> 		// Dummy GEM is the dummy GEM object I use to make the VM
> 		// participate in the locking without having to teach
> 		// drm_exec how to deal with raw dma_resv objects.
> 		ret = drm_exec_lock_obj(exec, vm->dummy_gem);
> 		drm_exec_retry_on_contention(exec);
> 		if (ret)
> 			return ret;
> 
> 		// Could take the form of drm_gpuva_sm_[un]map_acquire_locks()
> 		// helpers

Nevermind, I implemented a driver specific acquire_op_locks(), and it's
fairly simple with the gpuva iter (we just have to iterate over all VAs
covered by the operation range and call drm_exec_lock_obj() on the GEM
attached to these VAs), so it's probably not worth providing a generic
helper for that.