Re: [kvmarm] [PATCH v5 13/14] KVM: ARM: Handle I/O aborts

Will Deacon
2013-01-14T19:00:18Z

On Mon, Jan 14, 2013 at 06:53:14PM +0000, Alexander Graf wrote:
> On 01/14/2013 07:50 PM, Will Deacon wrote:
> > FWIW, KVM only needs this code for handling complex MMIO instructions, which
> > aren't even generated by recent guest kernels. I'm inclined to suggest removing
> > this emulation code from KVM entirely given that it's likely to bitrot as
> > it is executed less and less often.
>
> That'd mean that you heavily limit what type of guests you're executing,
> which I don't think is a good idea.

To be honest, I don't think we know whether that's true or not. How many
guests out there do writeback accesses to MMIO devices? Even on older
Linux guests, it was dependent on how GCC felt.

I see where you're coming from, I just don't think we can quantify it either
way outside of Linux.

Will