Re: [RFC/RFT PATCH v2 0/3] KVM: Introduce KVM_MEM_UNCACHED

[Andrew Jones <drjones@redhat.com>]

On Thu, May 14, 2015 at 11:37:46AM +0100, Peter Maydell wrote:
> On 14 May 2015 at 11:31, Andrew Jones <drjones@redhat.com> wrote:
> > Forgot to (4): switch from setting userspace's mapping to
> > device memory to normal, non-cacheable. Using device memory
> > caused a problem that Alex Graf found, and Peter Maydell suggested
> > using normal, non-cacheable instead.
> 
> Did you check that non-cacheable is definitely the correct
> kind of Normal memory attribute we want? (ie not write-through).

I was concerned that write-through wouldn't be sufficient. If the
guest writes to its non-cached memory, and QEMU needs to see what
it wrote, then won't write-through fail to work? Unless we some
how invalidate the cache first?

drew