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    SubjectRe: [PATCH] virtio_console: Stop doing DMA on the stack
    On Thu, Sep 08, 2016 at 08:49:43AM +0200, Ingo Molnar wrote:
    >
    > * Amit Shah <amit.shah@redhat.com> wrote:
    >
    > > On (Tue) 30 Aug 2016 [08:04:15], Andy Lutomirski wrote:
    > > > virtio_console uses a small DMA buffer for control requests. Move
    > > > that buffer into heap memory.
    > > >
    > > > Doing virtio DMA on the stack is normally okay on non-DMA-API virtio
    > > > systems (which is currently most of them), but it breaks completely
    > > > if the stack is virtually mapped.
    > > >
    > > > Tested by typing both directions using picocom aimed at /dev/hvc0.
    > > >
    > > > Signed-off-by: Andy Lutomirski <luto@kernel.org>
    > >
    > > Looks fine,
    > >
    > > Reviewed-by: Amit Shah <amit.shah@redhat.com>
    > >
    > > > ---
    > > >
    > > > Hi all-
    > > >
    > > > This is currently broken in tip:x86/asm. If you (Amit) like this patch,
    > > > would it make sense for Ingo to add it to -tip?
    > >
    > > Yes, I'm fine with that.
    >
    > Thanks! FYI, this patch now lives as:
    >
    > 9472fe7040bb ("virtio_console: Stop doing DMA on the stack")
    >
    > in tip:x86/asm, and is targeted for a v4.9 merge.
    >
    > Thanks,
    >
    > Ingo

    Thinking about it, maybe we should put it in 4.8
    after all, for benefit of systems using DMA API with virtio.
    Thoughts?

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