Messages in this thread | | | Date | Sat, 10 Sep 2016 06:33:48 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] virtio_console: Stop doing DMA on the stack |
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* Michael S. Tsirkin <mst@redhat.com> wrote:
> 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?
So CONFIG_VMAP_STACK=y is only going to be enabled for v4.9 - the enabling commit is part of tip:x86/asm as well. So AFAICS the commit is not strictly needed for v4.8.
Thanks,
Ingo
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