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Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api |
Date: |
Mon, 9 May 2016 13:09:24 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.1 |
On 28/04/2016 17:37, Michael S. Tsirkin wrote:
> > All the internally-emulated devices *can* be either translated or
> > untranslated. That's just a matter of software. Surely, you currently
> > *can't* have translated assigned devices (until someone implements the
> > whole VT-d page table shadowing or whatever), so you'll be barred from
> > assigning a device to a slot which *previously* had an untranslated
> > device. But so what? Put it in a different slot instead.
>
> Unfortunately people got used to be able to put any device
> in any slot, and built external tools around that ability.
> It's rather painful to break this assumption.
Once you move to PCIe, a lot of things become more complicated. This is
just one of them; instead of needing half a dozen PCI bridges, you'll
need half a dozen plus one.
Paolo