[lkml]   [2008]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [patch 2/8] x86 PAT: set VM_PFNMAP flag in vm_insert_pfn
On Fri, Nov 14, 2008 at 01:35:38PM -0800, Pallipadi, Venkatesh wrote:
> >-----Original Message-----
> >From: Nick Piggin []
> >Sent: Thursday, November 13, 2008 6:06 PM
> >To: Pallipadi, Venkatesh
> >Cc: Ingo Molnar; Thomas Gleixner; H Peter Anvin; Hugh Dickins;
> >Roland Dreier; Jesse Barnes; Jeremy Fitzhardinge; Arjan van de
> >Ven;; Siddha, Suresh B
> >Subject: Re: [patch 2/8] x86 PAT: set VM_PFNMAP flag in vm_insert_pfn
> >
> >On Thu, Nov 13, 2008 at 10:47:23AM -0800, Pallipadi, Venkatesh wrote:
> >>
> >> Yes. It does. But, it calls a lower level insert_pfn()
> >function. The lower
> >> level insert_pfn() does not have any bug checks. But the higher level
> >> vm_insert_pfn() checks for PFNMAP or MIXEDMAP.
> >
> >Yes, but is there anything extra you need to check for cache aliases in
> >MIXEDMAP mappings?
> >
> Yes. We need additional things to track MIXEDMAP and we are looking at that.
> But, that is slightly more trickier than the general PFNMAP case. And
> only in-tree user of MIXEDMAP is xip and that too it only uses it for
> regular WB mapping. So, we thought we should fix the more common case
> first here.
> With MIXEDMAP there is no way whether to distinguish whether insert_pfn
> Or insert_page was used while looking at VMA. We can probably use PFNMAP
> in addition to MIXEDMAP to indicate that, which will make things easier.

It's difficult because it can have either method for a single VMA, and
a given address in the vma may even change over time (not with current
code in kernel AFAIKS, but AXFS eventually might get to that point).

> But, we are still looking at that and trying to understand the change
> implication.

OK: now I understand correctly. Getting PFNMAP working is an important
first step. I agree.


 \ /
  Last update: 2008-11-17 03:33    [W:0.066 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site