linux-kernel - Re: [PATCH v3 7/7] dma-buf: system_heap: Add a system-uncached heap re-using the system heap

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Message-ID: <CALAqxLWSq3szE40hC_m-qpOOH1193jYLOT1_ZZh-eW9U0gnG8w@mail.gmail.com>
Date:   Wed, 7 Oct 2020 22:03:43 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Laura Abbott <labbott@...nel.org>,
        Brian Starkey <Brian.Starkey@....com>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Daniel Mentz <danielmentz@...gle.com>,
        Chris Goldsworthy <cgoldswo@...eaurora.org>,
        "??rjan Eide" <orjan.eide@....com>,
        Robin Murphy <robin.murphy@....com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Simon Ser <contact@...rsion.fr>,
        James Jones <jajones@...dia.com>,
        linux-media <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v3 7/7] dma-buf: system_heap: Add a system-uncached heap
 re-using the system heap

On Mon, Oct 5, 2020 at 6:45 AM Christoph Hellwig <hch@...radead.org> wrote:
>
> How is this going to deal with VIVT caches?

Hrm. That's a good question.   I'm not sure I totally have my head
around it but, I guess we could make sure to call
invalidate_kernel_vmap_range() in begin_cpu_access()  and
flush_kernel_vmap_range() in end_cpu_access() rather then exiting out
early as we do now?

Unless you have better guidance?

Worse case we could check CONFIG_CPU_CACHE_VIVT and not register the
system-uncached heap.

thanks
-john