On Thu, 18 Aug 2016 05:12:54 -0600 "Jan Beulich" <jbeul...@suse.com> wrote:
> >>> On 18.08.16 at 12:16, <andrew.coop...@citrix.com> wrote: > > On 18/08/16 11:06, Jan Beulich wrote: > >>>>> On 17.08.16 at 22:32, <konrad.w...@oracle.com> wrote: > >>> Looking at the kernel it assumes that WB is ok for 640KB->1MB. > >>> The comment says: > >>> " /* Low ISA region is always mapped WB in page table. No need to > >>> track > > *" > >> As per above it's not clear to me what this comment is backed by. > > > > This states what is in the pagetables. Not the combined result with MTRRs. > > > > WB in the pagetables and WC/UB in the MTRRs is a legal combination which > > functions correctly. > > True, but then again - haven't I been told multiple times that Linux > nowadays prefers to run without using MTRRs? The BIOS sets up the fixed MTRR registers for the 640K-1MB window. Those are separate to the variable range MTRR registers used for main memory with specific mappings for segments A000 to BFFF then C000-C7FF / C800-CFFF / etc up to FFFF. Alan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
