On 05/14/15 15:11, Peter Maydell wrote: > On 14 May 2015 at 14:03, Andrew Jones <drjo...@redhat.com> wrote: >> On Thu, May 14, 2015 at 11:37:46AM +0100, Peter Maydell wrote: >>> On 14 May 2015 at 11:31, Andrew Jones <drjo...@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? > > Well, I meant more that the correct mapping for userspace is > the same as the guest, whatever that is, and so somebody needs > to look at what the guest actually does
I think Ard explored this earlier, by tracking the MAIRs and stuff. Can't recall what the findings were though. (Or I could be simply confused, sorry.) Laszlo > rather than merely > hoping NormalNC is OK. (For instance, do we need to provide > support for QEMU to map both NC and writethrough?) > > -- PMM >
