Messages in this thread | | | Subject | Re: [Xen-devel] MTRR on Xen - BIOS use and implications for Linux | From | Toshi Kani <> | Date | Tue, 29 Mar 2016 16:14:41 -0600 |
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On Tue, 2016-03-29 at 10:22 -0700, Luis R. Rodriguez wrote: > On Thu, Mar 17, 2016 at 11:56 AM, Luis R. Rodriguez <mcgrof@kernel.org> > wrote: > > On Thu, Mar 17, 2016 at 11:13:03AM +0000, David Vrabel wrote: > > > On 16/03/16 20:08, Luis R. Rodriguez wrote: > > > > Toshi noted a while ago as well that if BIOS/firmware enables MTRR > > > > but the kernel does not have it enabled one issue might have been > > > > any MTRRs set up by the BIOS and ensuring the mapping is respected, > > To be clear the requirement expressed here was needing at least to > implement get_mtrr() on the Linux Xen guest side, it'd call the > already implemented hypercall XENPF_read_memtype in turn. Toshi had > hinted this was perhaps needed on the Linux Xen guest side given that > the BIOS may have set up MTRRs on its own, so we needed the guest to > be able to get the right type for a particular range. More on that > below
No, I did not say that. :-) I said it because you mentioned that you wanted to disable MTRRs even though BIOS enabled MTRRs.
My point is that the kernel should not change the MTRR setup. That is: - If BIOS enables MTRRs, then kernel needs to keep them enabled. - If BIOS disables MTRRs, then the kernel needs to keep them disabled.
Therefore, the kernel can keep MTRRs disabled on Xen guests.
I think you repeated the same questions in this email, so please refer my previous reply for the rest.
Thanks, -Toshi
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