On 28 February 2017 at 21:58, Andrew Baumann <andrew.baum...@microsoft.com> wrote: > On a successful long-descriptor translation, PAR_EL1 bits 56:63 are > expected to report the memory attributes of the page. However, the > page table walker (get_phys_addr()) does not currently retrieve these > attributes. Rather than leaving these bits clear (which implies > uncacheable device memory), this change sets them to 0xff, which > corresponds to write-back cached normal memory. > > Signed-off-by: Andrew Baumann <andrew.baum...@microsoft.com> > --- > In my (biased!) opinion, this is a better lie to tell for an emulated > environment. It also happens to un-break the Windows boot process, and > enable an NT kernel optimisation (DC ZVA for page zeroing).
It's not clear to me that misreporting Device memory as Normal is any better than misreporting Normal memory as Device -- at least, it seems like it might break currently working guests. I think it would be safer to implement the PAR as "honour the attribute index bits in page table descriptors and return the corresponding bits from the MAIR registers". thanks -- PMM
