Re: [PATCH 2/2] adreno: Detect shutdown during get_param()

[Akhil P Oommen <quic_akhilpo@quicinc.com>]

On 11/12/2022 1:19 AM, Joel Fernandes (Google) wrote:
> Even though the GPU is shut down, during kexec reboot we can have userspace
> still running. This is especially true if KEXEC_JUMP is not enabled, because we
> do not freeze userspace in this case.
>
> To prevent crashes, track that the GPU is shutdown and prevent get_param() from
> accessing GPU resources if we find it shutdown.
>
> This fixes the following crash during kexec reboot on an ARM64 device with adreno GPU:
>
> [  292.534314] Kernel panic - not syncing: Asynchronous SError Interrupt
> [  292.534323] Hardware name: Google Lazor (rev3 - 8) with LTE (DT)
> [  292.534326] Call trace:
> [  292.534328]  dump_backtrace+0x0/0x1d4
> [  292.534337]  show_stack+0x20/0x2c
> [  292.534342]  dump_stack_lvl+0x60/0x78
> [  292.534347]  dump_stack+0x18/0x38
> [  292.534352]  panic+0x148/0x3b0
> [  292.534357]  nmi_panic+0x80/0x94
> [  292.534364]  arm64_serror_panic+0x70/0x7c
> [  292.534369]  do_serror+0x0/0x7c
> [  292.534372]  do_serror+0x54/0x7c
> [  292.534377]  el1h_64_error_handler+0x34/0x4c
> [  292.534381]  el1h_64_error+0x7c/0x80
> [  292.534386]  el1_interrupt+0x20/0x58
> [  292.534389]  el1h_64_irq_handler+0x18/0x24
> [  292.534395]  el1h_64_irq+0x7c/0x80
> [  292.534399]  local_daif_inherit+0x10/0x18
> [  292.534405]  el1h_64_sync_handler+0x48/0xb4
> [  292.534410]  el1h_64_sync+0x7c/0x80
> [  292.534414]  a6xx_gmu_set_oob+0xbc/0x1fc
> [  292.534422]  a6xx_get_timestamp+0x40/0xb4
> [  292.534426]  adreno_get_param+0x12c/0x1e0
> [  292.534433]  msm_ioctl_get_param+0x64/0x70
> [  292.534440]  drm_ioctl_kernel+0xe8/0x158
> [  292.534448]  drm_ioctl+0x208/0x320
> [  292.534453]  __arm64_sys_ioctl+0x98/0xd0
> [  292.534461]  invoke_syscall+0x4c/0x118
> [  292.534467]  el0_svc_common+0x98/0x104
> [  292.534473]  do_el0_svc+0x30/0x80
> [  292.534478]  el0_svc+0x20/0x50
> [  292.534481]  el0t_64_sync_handler+0x78/0x108
> [  292.534485]  el0t_64_sync+0x1a4/0x1a8
> [  292.534632] Kernel Offset: 0x1a5f800000 from 0xffffffc008000000
> [  292.534635] PHYS_OFFSET: 0x80000000
> [  292.534638] CPU features: 0x40018541,a3300e42
> [  292.534644] Memory Limit: none
>
> Cc: Rob Clark <robdclark@chromium.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ricardo Ribalda <ribalda@chromium.org>
> Cc: Ross Zwisler <zwisler@kernel.org>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
>   drivers/gpu/drm/msm/adreno/adreno_device.c | 1 +
>   drivers/gpu/drm/msm/adreno/adreno_gpu.c    | 2 +-
>   drivers/gpu/drm/msm/msm_gpu.h              | 3 +++
>   3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
> index f0cff62812c3..03d912dc0130 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> @@ -612,6 +612,7 @@ static void adreno_shutdown(struct platform_device *pdev)
>   {
>   	struct msm_gpu *gpu = dev_to_gpu(&pdev->dev);
>   
> +	gpu->is_shutdown = true;
>   	WARN_ON_ONCE(adreno_system_suspend(&pdev->dev));
>   }
>   
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index 382fb7f9e497..6903c6892469 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -251,7 +251,7 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
>   	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>   
>   	/* No pointer params yet */
> -	if (*len != 0)
> +	if (*len != 0 || gpu->is_shutdown)
>   		return -EINVAL;
This will race with shutdown. Probably, propagating back the return 
value of pm_runtime_get() in every possible ioctl call path is the right 
thing to do.

I have never thought about this scenario. Do you know why userspace is 
not freezed before kexec?

-Akhil.
>   
>   	switch (param) {
> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> index ff911e7305ce..f18b0a91442b 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.h
> +++ b/drivers/gpu/drm/msm/msm_gpu.h
> @@ -214,6 +214,9 @@ struct msm_gpu {
>   	/* does gpu need hw_init? */
>   	bool needs_hw_init;
>   
> +	/* is the GPU shutdown? */
> +	bool is_shutdown;
> +
>   	/**
>   	 * global_faults: number of GPU hangs not attributed to a particular
>   	 * address space