[AMD Official Use Only - General] Hey Alex, Sure, I will pick it up and push it to staging.
Regards Shashank ________________________________ From: Alex Deucher <alexdeuc...@gmail.com> Sent: Monday, March 25, 2024 12:23 AM To: Sharma, Shashank <shashank.sha...@amd.com> Cc: Johannes Weiner <han...@cmpxchg.org>; Christian König <ckoenig.leichtzumer...@gmail.com>; Deucher, Alexander <alexander.deuc...@amd.com>; Koenig, Christian <christian.koe...@amd.com>; amd-...@lists.freedesktop.org <amd-...@lists.freedesktop.org>; dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>; linux-ker...@vger.kernel.org <linux-ker...@vger.kernel.org> Subject: Re: [PATCH] drm/amdgpu: fix deadlock while reading mqd from debugfs On Sat, Mar 23, 2024 at 4:47 PM Sharma, Shashank <shashank.sha...@amd.com> wrote: > > > On 23/03/2024 15:52, Johannes Weiner wrote: > > On Thu, Mar 14, 2024 at 01:09:57PM -0400, Johannes Weiner wrote: > >> Hello, > >> > >> On Fri, Mar 08, 2024 at 12:32:33PM +0100, Christian König wrote: > >>> Am 07.03.24 um 23:07 schrieb Johannes Weiner: > >>>> Lastly I went with an open loop instead of a memcpy() as I wasn't > >>>> sure if that memory is safe to address a byte at at time. > >> Shashank pointed out to me in private that byte access would indeed be > >> safe. However, after actually trying it it won't work because memcpy() > >> doesn't play nice with mqd being volatile: > >> > >> /home/hannes/src/linux/linux/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c: In > >> function 'amdgpu_debugfs_mqd_read': > >> /home/hannes/src/linux/linux/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c:550:22: > >> warning: passing argument 1 of '__builtin_dynamic_object_size' discards > >> 'volatil' qualifier from pointer target type [-Wdiscarded-qualifiers] > >> 550 | memcpy(kbuf, mqd, ring->mqd_size); > >> > >> So I would propose leaving the patch as-is. Shashank, does that sound > >> good to you? > > Friendly ping :) > > > > Shashank, is your Reviewed-by still good for this patch, given the > > above? > > Ah, sorry I missed this due to some parallel work, and just realized the > memcpy/volatile limitation. > > I also feel the need of protecting MQD read under a lock to avoid > parallel change in MQD while we do byte-by-byte copy, but I will add > that in my to-do list. > > Please feel free to use my R-b. Shashank, if the patch looks good, can you pick it up and apply it? Alex > > - Shashank > > > Thanks
