Messages in this thread | | | Date | Tue, 28 Sep 2010 12:05:19 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 12/12] xen/mtrr: Add mtrr_if support for Xen mtrr |
| |
On 09/28/2010 11:58 AM, Jeremy Fitzhardinge wrote: > On 09/28/2010 11:46 AM, H. Peter Anvin wrote: >> Well, we're specifically talking about a virtual machine which has >> direct access to hardware, so it is concerned about the real physical >> memory properties of real physical pages. If we can assume that >> BIOS/Xen will always set up MTRR correctly then there shouldn't be any >> need for the kernel to modify the MTRR itself. How true is that in >> general? I don't know, but if we could rely on BIOS then there'd never >> be a need to touch MTRR, would there? >> Well, in the past MTRRs were abused for device properties mainly by the >> X server, but other than that, no, not really. The other thing we do is >> the MTRR cleanup (which doesn't involve /proc/mtrr) to deal with >> brokenness in the BIOS setup, but that really belongs in the hypervisor >> in your case since it fundamentally affects how memory is handled. > > Yeah, the hypervisor should definitely deal with that. I have no > problem in principle with leaving MTRRs entirely to Xen, but I was just > concerned about possible repercussions. Certainly when I first did this > work, I was using Fedora 8 whose X server did depend on /proc/mtrr for > good performance. >
Yeah, that should all be fixed now.
-hpa
| |