Re: [Qemu-devel] [PATCH v3] hw/arm/virt: Add high MMIO PCI region

[Peter Maydell]

On 29 July 2015 at 12:16, Pavel Fedin <address@hidden> wrote:
>> I don't really want to have two different address layouts
>> just to work around a kernel bug
>
>  They will not be really different. Just for 32-bit machines
> there will be no second MMIO window, and for 64-bit ones there
> will be. Nothing else will be different.

That's still a difference. (Also, even a 32-bit guest might
have a 40-bit physical address space and be potentially able
to use an upper MMIO window.)

>> if we could fix the kernel bug instead...
>
>  We could. But what about existing installations? They will be forced to 
> upgrade kernels, we will not have backwards compatibility option. And users 
> will complain that "my old VM stopped working with new qemu".
>  Well, this discussion seems to be stuck, so let's move on.
> What is your final word?

(1) We should confirm whether this really is a guest kernel
bug (as opposed to the device tree QEMU emits not being
in spec)
(2) If it is a kernel bug, submit a patch to fix it
(3) Consider a workaround for older guests anyway. The
scope of that workaround would depend on exactly which
guests are affected, which is presumably something we
figured out during step (1).

thanks
-- PMM