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From: Javier Martinez Canillas <javierm@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>, "Peng Fan (OSS)"
 <peng.fan@oss.nxp.com>, Maarten Lankhorst
 <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>,
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>
Cc: Peng Fan <peng.fan@nxp.com>, dri-devel@lists.freedesktop.org,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/fbdev-dma: fix getting smem_start
In-Reply-To: <e307fdc0-553d-4946-9017-ed3a28e9cae2@suse.de>
References: <20240604080328.4024838-1-peng.fan@oss.nxp.com>
 <8f4a6d80-dd3e-422f-88af-d26f50c973ff@suse.de>
 <e307fdc0-553d-4946-9017-ed3a28e9cae2@suse.de>
Date: Wed, 12 Jun 2024 09:49:46 +0200
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Thomas Zimmermann <tzimmermann@suse.de> writes:

Hello Thomas,

> Hi
>
> Am 10.06.24 um 10:47 schrieb Thomas Zimmermann:
>> Hi
>>
>> Am 04.06.24 um 10:03 schrieb Peng Fan (OSS):
>>> From: Peng Fan <peng.fan@nxp.com>
>>>
>>> If 'info->screen_buffer' locates in vmalloc address space, virt_to_page
>>> will not be able to get correct results. With CONFIG_DEBUG_VM and
>>> CONFIG_DEBUG_VIRTUAL enabled on ARM64, there is dump below:
>>
>> Which graphics driver triggers this bug?
>>
>>> [=C2=A0=C2=A0=C2=A0 3.536043] ------------[ cut here ]------------
>>> [=C2=A0=C2=A0=C2=A0 3.540716] virt_to_phys used for non-linear address:=
=20
>>> 000000007fc4f540 (0xffff800086001000)
>>> [=C2=A0=C2=A0=C2=A0 3.552628] WARNING: CPU: 4 PID: 61 at arch/arm64/mm/=
physaddr.c:12=20
>>> __virt_to_phys+0x68/0x98
>>> [=C2=A0=C2=A0=C2=A0 3.565455] Modules linked in:
>>> [=C2=A0=C2=A0=C2=A0 3.568525] CPU: 4 PID: 61 Comm: kworker/u12:5 Not ta=
inted=20
>>> 6.6.23-06226-g4986cc3e1b75-dirty #250
>>> [=C2=A0=C2=A0=C2=A0 3.577310] Hardware name: NXP i.MX95 19X19 board (DT)
>>> [=C2=A0=C2=A0=C2=A0 3.582452] Workqueue: events_unbound deferred_probe_=
work_func
>>> [=C2=A0=C2=A0=C2=A0 3.588291] pstate: 60400009 (nZCv daif +PAN -UAO -TC=
O -DIT -SSBS=20
>>> BTYPE=3D--)
>>> [=C2=A0=C2=A0=C2=A0 3.595233] pc : __virt_to_phys+0x68/0x98
>>> [=C2=A0=C2=A0=C2=A0 3.599246] lr : __virt_to_phys+0x68/0x98
>>> [=C2=A0=C2=A0=C2=A0 3.603276] sp : ffff800083603990
>>> [=C2=A0=C2=A0=C2=A0 3.677939] Call trace:
>>> [=C2=A0=C2=A0=C2=A0 3.680393]=C2=A0 __virt_to_phys+0x68/0x98
>>> [=C2=A0=C2=A0=C2=A0 3.684067]=C2=A0 drm_fbdev_dma_helper_fb_probe+0x138=
/0x238
>>> [=C2=A0=C2=A0=C2=A0 3.689214] __drm_fb_helper_initial_config_and_unlock=
+0x2b0/0x4c0
>>> [=C2=A0=C2=A0=C2=A0 3.695385]=C2=A0 drm_fb_helper_initial_config+0x4c/0=
x68
>>> [=C2=A0=C2=A0=C2=A0 3.700264]=C2=A0 drm_fbdev_dma_client_hotplug+0x8c/0=
xe0
>>> [=C2=A0=C2=A0=C2=A0 3.705161]=C2=A0 drm_client_register+0x60/0xb0
>>> [=C2=A0=C2=A0=C2=A0 3.709269]=C2=A0 drm_fbdev_dma_setup+0x94/0x148
>>>
>>> So add a check 'is_vmalloc_addr'.
>>>
>>> Fixes: b79fe9abd58b ("drm/fbdev-dma: Implement fbdev emulation for=20
>>> GEM DMA helpers")
>>> Signed-off-by: Peng Fan <peng.fan@nxp.com>
>>
>> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
>
> I'm taking back my r-b. The memory is expected to by be physically=20
> contiguous and vmalloc() won't guarantee that.
>

Agreed.

> Best regards
> Thomas
>

--=20
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat