From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Guillaume.Gardet@arm.com, David Airlie <airlied@linux.ie>,
open list <linux-kernel@vger.kernel.org>,
stable@vger.kernel.org, gurchetansingh@chromium.org,
dri-devel@lists.freedesktop.org, tzimmermann@suse.de
Subject: Re: [PATCH v5 1/3] drm/shmem: add support for per object caching flags.
Date: Thu, 27 Feb 2020 13:16:45 +0100 [thread overview]
Message-ID: <68a05ace-40bc-76d6-5464-2c96328874b9@shipmail.org> (raw)
In-Reply-To: <20200227105643.h4klc3ybhpwv2l3x@sirius.home.kraxel.org>
On 2/27/20 11:56 AM, Gerd Hoffmann wrote:
> Hi,
>
>> I think it might be safe for some integrated graphics where the driver
>> maintainers can guarantee that it's safe on all particular processors used
>> with that driver, but then IMO it should be moved out to those drivers.
>>
>> Other drivers needing write-combine shouldn't really use shmem.
>>
>> So again, to fix the regression, could we revert 0be895893607f ("drm/shmem:
>> switch shmem helper to &drm_gem_object_funcs.mmap") or does that have other
>> implications?
> This patch isn't a regression. The old code path has the
> pgprot_writecombine() call in drm_gem_mmap_obj(), so the behavior
> is the same before and afterwards.
OK. I wasn't checking where this all came from from the start...
> But with the patch in place we can easily have shmem helpers do their
> own thing instead of depending on whatever drm_gem_mmap_obj() is doing.
> Just using cached mappings unconditionally would be perfectly fine for
> virtio-gpu.
>
> Not sure about the other users though. I'd like to fix the virtio-gpu
> regression (coming from ttm -> shmem switch) asap, and I don't feel like
> changing the behavior for other drivers in 5.6-rc is a good idea.
>
> So I'd like to push patches 1+2 to -fixes and sort everything else later
> in -next. OK?
OK with me. Do we have any idea what drivers are actually using
write-combine and decrypted?
/Thomas
>
> cheers,
> Gerd
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next prev parent reply other threads:[~2020-02-27 12:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 15:47 [PATCH v5 0/3] drm/virtio: fix mmap page attributes Gerd Hoffmann
2020-02-26 15:47 ` [PATCH v5 1/3] drm/shmem: add support for per object caching flags Gerd Hoffmann
2020-02-26 16:51 ` Guillaume Gardet
2020-02-26 18:24 ` Thomas Hellström (VMware)
2020-02-27 0:02 ` Chia-I Wu
2020-02-27 7:16 ` Thomas Hellström (VMware)
2020-02-27 7:53 ` Gerd Hoffmann
2020-02-27 8:10 ` Thomas Hellström (VMware)
2020-02-27 10:56 ` Gerd Hoffmann
2020-02-27 12:16 ` Thomas Hellström (VMware) [this message]
2020-02-27 13:21 ` Gerd Hoffmann
2020-02-27 13:44 ` Thomas Hellström (VMware)
2020-02-27 13:49 ` Thomas Hellström (VMware)
2020-02-28 9:49 ` Gerd Hoffmann
2020-02-28 9:54 ` Thomas Hellström (VMware)
2020-02-28 10:46 ` Gerd Hoffmann
2020-03-02 1:56 ` Qiang Yu
2020-02-26 15:47 ` [PATCH v5 2/3] drm/virtio: fix mmap page attributes Gerd Hoffmann
2020-02-26 16:52 ` Guillaume Gardet
2020-02-26 15:47 ` [PATCH v5 3/3] drm/udl: simplify gem object mapping Gerd Hoffmann
2020-02-26 17:03 ` [PATCH v5 0/3] drm/virtio: fix mmap page attributes Gurchetan Singh
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