From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
To: "Rob Clark" <robdclark@gmail.com>,
"Christian König" <christian.koenig@amd.com>,
"David Airlie" <airlied@linux.ie>,
"Gerd Hoffmann" <kraxel@redhat.com>,
"Gurchetan Singh" <gurchetansingh@chromium.org>,
"Chia-I Wu" <olvaffe@gmail.com>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Maxime Ripard" <mripard@kernel.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"Emil Velikov" <emil.l.velikov@gmail.com>,
"Thomas Hellström" <thomas_os@shipmail.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
"open list:VIRTIO GPU DRIVER"
<virtualization@lists.linux-foundation.org>,
linux-tegra@vger.kernel.org, "Dmitry Osipenko" <digetx@gmail.com>,
kernel@collabora.com
Cc: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH v8 2/2] drm/gem: Don't map imported GEMs
Date: Wed, 10 Aug 2022 22:26:11 +0300 [thread overview]
Message-ID: <9674d00e-c0d6-ceba-feab-5dc475bda694@collabora.com> (raw)
In-Reply-To: <CAF6AEGvfAJgwBe4+sK0gAkZ++MwH9x4=698C8XSnmfYNMFZqfA@mail.gmail.com>
On 8/10/22 18:08, Rob Clark wrote:
> On Wed, Aug 10, 2022 at 4:47 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>>
>> On Wed, Jul 06, 2022 at 10:02:07AM +0300, Dmitry Osipenko wrote:
>>> On 7/6/22 00:48, Rob Clark wrote:
>>>> On Tue, Jul 5, 2022 at 4:51 AM Christian König <christian.koenig@amd.com> wrote:
>>>>>
>>>>> Am 01.07.22 um 11:02 schrieb Dmitry Osipenko:
>>>>>> Drivers that use drm_gem_mmap() and drm_gem_mmap_obj() helpers don't
>>>>>> handle imported dma-bufs properly, which results in mapping of something
>>>>>> else than the imported dma-buf. On NVIDIA Tegra we get a hard lockup when
>>>>>> userspace writes to the memory mapping of a dma-buf that was imported into
>>>>>> Tegra's DRM GEM.
>>>>>>
>>>>>> Majority of DRM drivers prohibit mapping of the imported GEM objects.
>>>>>> Mapping of imported GEMs require special care from userspace since it
>>>>>> should sync dma-buf because mapping coherency of the exporter device may
>>>>>> not match the DRM device. Let's prohibit the mapping for all DRM drivers
>>>>>> for consistency.
>>>>>>
>>>>>> Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>>>>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>>>>>
>>>>> I'm pretty sure that this is the right approach, but it's certainly more
>>>>> than possible that somebody abused this already.
>>>>
>>>> I suspect that this is abused if you run deqp cts on android.. ie. all
>>>> winsys buffers are dma-buf imports from gralloc. And then when you
>>>> hit readpix...
>>>>
>>>> You might only hit this in scenarios with separate gpu and display (or
>>>> dGPU+iGPU) because self-imports are handled differently in
>>>> drm_gem_prime_import_dev().. and maybe not in cases where you end up
>>>> with a blit from tiled/compressed to linear.. maybe that narrows the
>>>> scope enough to just fix it in userspace?
>>>
>>> Given that that only drivers which use DRM-SHMEM potentially could've
>>> map imported dma-bufs (Panfrost, Lima) and they already don't allow to
>>> do that, I think we're good.
>>
>> So can I have an ack from Rob here or are there still questions that this
>> might go boom?
>>
>> Dmitry, since you have a bunch of patches merged now I think would also be
>> good to get commit rights so you can drive this more yourself. I've asked
>> Daniel Stone to help you out with getting that.
>
> I *think* we'd be ok with this on msm, mostly just by dumb luck.
> Because the dma-buf's we import will be self-import. I'm less sure
> about panfrost (src/panfrost/lib/pan_bo.c doesn't seem to have a
> special path for imported dma-bufs either, and in that case they won't
> be self-imports.. but I guess no one has tried to run android cts on
> panfrost).
The last time I tried to mmap dma-buf imported to Panfrost didn't work
because Panfrost didn't implement something needed for that. I'll need
to take a look again because can't recall what it was.
> What about something less drastic to start, like (apologies for
> hand-edited patch):
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 86d670c71286..fc9ec42fa0ab 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -1034,6 +1034,10 @@ int drm_gem_mmap_obj(struct drm_gem_object
> *obj, unsigned long obj_size,
> {
> int ret;
>
> + WARN_ON_ONCE(obj->import_attach);
This will hang NVIDIA Tegra, which is what this patch fixed initially.
If neither of upstream DRM drivers need to map imported dma-bufs and
never needed, then why do we need this?
--
Best regards,
Dmitry
next prev parent reply other threads:[~2022-08-10 19:26 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-01 9:02 [PATCH v8 0/2] DRM GEM fixes Dmitry Osipenko
2022-07-01 9:02 ` [PATCH v8 1/2] drm/gem: Properly annotate WW context on drm_gem_lock_reservations() error Dmitry Osipenko
2022-07-05 11:33 ` Christian König
2022-08-09 16:44 ` Daniel Vetter
2022-08-10 6:52 ` Christian König
2022-08-10 8:33 ` Daniel Vetter
2022-08-10 9:04 ` Christian König
2022-07-01 9:02 ` [PATCH v8 2/2] drm/gem: Don't map imported GEMs Dmitry Osipenko
2022-07-05 11:39 ` Christian König
2022-07-05 21:48 ` Rob Clark
2022-07-06 7:02 ` Dmitry Osipenko
2022-08-10 11:47 ` Daniel Vetter
2022-08-10 15:08 ` Rob Clark
2022-08-10 19:26 ` Dmitry Osipenko [this message]
2022-08-10 22:03 ` Rob Clark
2022-08-10 22:23 ` Dmitry Osipenko
2022-08-10 23:19 ` Rob Clark
2022-08-12 11:26 ` Dmitry Osipenko
2022-08-12 14:57 ` Rob Clark
2022-08-12 15:01 ` Rob Clark
2022-08-16 11:44 ` Dmitry Osipenko
2022-08-16 11:52 ` Dmitry Osipenko
2022-08-16 12:03 ` Christian König
2022-08-16 19:55 ` Dmitry Osipenko
2022-08-22 17:26 ` Dmitry Osipenko
2022-08-23 10:01 ` Christian König
2022-08-23 16:47 ` Rob Clark
2022-09-07 10:25 ` Dmitry Osipenko
2022-09-11 18:00 ` Rob Clark
2022-08-16 22:18 ` Rob Clark
2022-08-10 19:27 ` Dmitry Osipenko
2022-07-22 11:49 ` [PATCH v8 0/2] DRM GEM fixes Dmitry Osipenko
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