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Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other o
From: |
Rusty Russell |
Subject: |
Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out |
Date: |
Tue, 31 Jul 2012 09:17:11 +0930 |
User-agent: |
Notmuch/0.12 (http://notmuchmail.org) Emacs/23.3.1 (i686-pc-linux-gnu) |
On Mon, 30 Jul 2012 11:01:20 -0500, Anthony Liguori <address@hidden> wrote:
> Avi Kivity <address@hidden> writes:
> > It doesn't seem to be such a huge problem, though it does turn virtio
> > into a respec'ed PCI.
>
> Virtio was originally designed to be a DMA API (although not ABI). From
> a virtio-pci perspective, adding a large memory area that can be
> referenced is not a big deal at all. You can take PFNs into the memory
> area and just handle it like you would any other address reference.
>
> But for the virtio API within Linux, it presents a challenge.
> Originally, there was a desire to support DMA-based interfaces like
> Xen's grant tables or PowerVM's TCE transfers.
>
> While there have been proof of concepts, it's never landed in an
> upstream kernel. I'd be perfectly happy forcing the virtio API to
> assume the ability to share large areas of memory between the host and
> guest and eliminate the possibility to support all types of hypervisors
> for some devices.
>
> (While Xen supports shared memory, PowerVM does not--I don't give a damn
> about supporting PowerVM FWIW).
>
> Rusty, what do you think about the above?
Shared memory is an efficiency thing, not a requirement. If the virtio
side-channel tells the device about the location of framebuffer
changes, it could still be quite efficient.
Cheers,
Rusty.
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, (continued)
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Anthony Liguori, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Avi Kivity, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Anthony Liguori, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Avi Kivity, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Anthony Liguori, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Avi Kivity, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Anthony Liguori, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out,
Rusty Russell <=
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Benjamin Herrenschmidt, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Alon Levy, 2012/07/31
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Benjamin Herrenschmidt, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Anthony Liguori, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Benjamin Herrenschmidt, 2012/07/30
- Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Alon Levy, 2012/07/30
Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, Blue Swirl, 2012/07/30
Re: [Qemu-devel] Cirrus bugs vs endian: how two bugs cancel each other out, ronnie sahlberg, 2012/07/31