[PATCH] drm/amdgpu: fix kernel page fault issue by ras recovery on sGPU

[Pan, Xinhui]

that breaks the device list in gpu recovery.
________________________________
From: Pan, Xinhui <Xinhui.Pan at amd.com>
Sent: Friday, April 17, 2020 7:11:40 PM
To: Chen, Guchun <Guchun.Chen at amd.com>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>; Zhang, Hawking <Hawking.Zhang at amd.com>; Li, Dennis <Dennis.Li at amd.com>; Clements, John <John.Clements at amd.com>; Koenig, Christian <Christian.Koenig at amd.com>
Subject: Re: [PATCH] drm/amdgpu: fix kernel page fault issue by ras recovery on sGPU

This patch shluld fix the panic.

but I would like you do NOT add adev xgmi head to the local device list. if ras ue occurs while the gpu is already in gpu recovery.
________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Christian König <ckoenig.leichtzumerken at gmail.com>
Sent: Friday, April 17, 2020 5:17:22 PM
To: Chen, Guchun <Guchun.Chen at amd.com>; amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>; Zhang, Hawking <Hawking.Zhang at amd.com>; Li, Dennis <Dennis.Li at amd.com>; Clements, John <John.Clements at amd.com>
Subject: Re: [PATCH] drm/amdgpu: fix kernel page fault issue by ras recovery on sGPU

Am 16.04.20 um 17:47 schrieb Guchun Chen:
> When running ras uncorrectable error injection and trigger GPU
> reset on sGPU, below issue is observed. It's caused by the list
> uninitialized when accessing.
>
> [   80.047227] BUG: unable to handle page fault for address: ffffffffc0f4f750
> [   80.047300] #PF: supervisor write access in kernel mode
> [   80.047351] #PF: error_code(0x0003) - permissions violation
> [   80.047404] PGD 12c20e067 P4D 12c20e067 PUD 12c210067 PMD 41c4ee067 PTE 404316061
> [   80.047477] Oops: 0003 [#1] SMP PTI
> [   80.047516] CPU: 7 PID: 377 Comm: kworker/7:2 Tainted: G           OE     5.4.0-rc7-guchchen #1
> [   80.047594] Hardware name: System manufacturer System Product Name/TUF Z370-PLUS GAMING II, BIOS 0411 09/21/2018
> [   80.047888] Workqueue: events amdgpu_ras_do_recovery [amdgpu]
>
> Signed-off-by: Guchun Chen <guchun.chen at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> index b27d9d62c9df..260b4a42e0ae 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
> @@ -1448,9 +1448,10 @@ static void amdgpu_ras_do_recovery(struct work_struct *work)
>        struct amdgpu_hive_info *hive = amdgpu_get_xgmi_hive(adev, false);
>
>        /* Build list of devices to query RAS related errors */
> -     if  (hive && adev->gmc.xgmi.num_physical_nodes > 1) {
> +     if  (hive && adev->gmc.xgmi.num_physical_nodes > 1)
>                device_list_handle = &hive->device_list;
> -     } else {
> +     else {

The coding style here is incorrect. If one branch of an if/else uses {}
the other(s) should use it as well.

> +             INIT_LIST_HEAD(&device_list);

That was suggested before but then reverted, but I'm not sure why.

Regards,
Christian.

>                list_add_tail(&adev->gmc.xgmi.head, &device_list);
>                device_list_handle = &device_list;
>        }

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