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Date:   Thu, 17 Dec 2020 10:55:42 +0100
Message-ID: <s5h5z50n4dd.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Lars-Peter Clausen <lars@metafoo.de>
Cc:     Robin Gong <yibin.gong@nxp.com>, perex@perex.cz, tiwai@suse.com,
        akpm@linux-foundation.org, xiang@kernel.org,
        pierre-louis.bossart@linux.intel.com, gustavoars@kernel.org,
        shengjiu.wang@nxp.com, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 ] ALSA: core: memalloc: add page alignment for iram
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References: <1608221747-3474-1-git-send-email-yibin.gong@nxp.com>
        <05c824e5-0c33-4182-26fa-b116a42b10d6@metafoo.de>
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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