linux-kernel - Re: [PATCH 2/3] drm/msm: Allocate memory for disp snapshot with kvzalloc()

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Message-ID: <00e4015e-9dcb-4a05-90a4-0bca62c3b0a2@quicinc.com>
Date: Mon, 14 Oct 2024 11:56:20 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Douglas Anderson <dianders@...omium.org>, Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Stephen Boyd <swboyd@...omium.org>, David Airlie <airlied@...il.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Sean Paul <sean@...rly.run>, Simona Vetter <simona@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] drm/msm: Allocate memory for disp snapshot with
 kvzalloc()



On 10/14/2024 9:36 AM, Douglas Anderson wrote:
> With the "drm/msm: add a display mmu fault handler" series [1] we saw
> issues in the field where memory allocation was failing when
> allocating space for registers in msm_disp_state_dump_regs().
> Specifically we were seeing an order 5 allocation fail. It's not
> surprising that order 5 allocations will sometimes fail after the
> system has been up and running for a while.
> 
> There's no need here for contiguous memory. Change the allocation to
> kvzalloc() which should make it much less likely to fail.
> 
> [1] https://lore.kernel.org/r/20240628214848.4075651-1-quic_abhinavk@quicinc.com/
> 
> Fixes: 98659487b845 ("drm/msm: add support to take dpu snapshot")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>   drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 

I had some doubts on how this issue happens considering that the devcore 
should automatically release the memory within 5 sec even if userspace 
had not read this. So there is no leak as such, its just that in a 
heavily loaded system, this can happen.

Fix looks okay to me,

Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>