linux-kernel - Re: [PATCH v1 ] ALSA: core: memalloc: add page alignment for iram

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Date:   Thu, 17 Dec 2020 10:55:42 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Lars-Peter Clausen <lars@...afoo.de>
Cc:     Robin Gong <yibin.gong@....com>, perex@...ex.cz, tiwai@...e.com,
        akpm@...ux-foundation.org, xiang@...nel.org,
        pierre-louis.bossart@...ux.intel.com, gustavoars@...nel.org,
        shengjiu.wang@....com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 ] ALSA: core: memalloc: add page alignment for iram

On Thu, 17 Dec 2020 10:43:45 +0100,
Lars-Peter Clausen wrote:
> 
> On 12/17/20 5:15 PM, Robin Gong wrote:
> > Since mmap for userspace is based on page alignment, add page alignment
> > for iram alloc from pool, otherwise, some good data located in the same
> > page of dmab->area maybe touched wrongly by userspace like pulseaudio.
> >
> I wonder, do we also have to align size to be a multiple of PAGE_SIZE
> to avoid leaking unrelated data?

Hm, a good question.  Basically the PCM buffer size itself shouldn't
be influenced by that (i.e. no hw-constraint or such is needed), but
the padding should be cleared indeed.  I somehow left those to the
allocator side, but maybe it's safer to clear the whole buffer in
sound/core/memalloc.c commonly.


thanks,

Takashi