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Date:   Wed, 17 May 2023 01:08:42 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Sumit Garg <sumit.garg@linaro.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Xiaoming Ding <xiaoming.ding@mediatek.com>,
        Jens Wiklander <jens.wiklander@linaro.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        op-tee@lists.trustedfirmware.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, fei.xu@mediatek.com,
        srv_heupstream@mediatek.com, linux-mm@kvack.org
Subject: Re: [PATCH] tee: add FOLL_LONGTERM for CMA case when alloc shm
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On Wed, May 17, 2023 at 01:22:51PM +0530, Sumit Garg wrote:
> > > +#if IS_ENABLED(CONFIG_CMA)
> > > +     page_flag |= FOLL_LONGTERM;
> > > +#endif
> > >       if (flags & TEE_SHM_USER_MAPPED)
> >
> > If this mapping is long live it should always use FOLL_LONGTERM.
> 
> It depends on the userspace application needs. However, I think it
> should be safe to use FOLL_LONGTERM by default to serve cases like
> secure media playback.

long term is defined as won't automatically go away during the same
syscall.