lkml.org 
[lkml]   [2014]   [Jul]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC PATCH 0/11] Support Write-Through mapping on x86
From
Date

On Mon, 2014-07-21 at 09:47 -0700, H. Peter Anvin wrote:
> On 07/21/2014 09:31 AM, Toshi Kani wrote:
> > Do you have any comments / suggestions for this approach?
>
> Approach to what, specifically?
>
> Keep in mind the PAT bit is different for large pages. This needs to be
> dealt with.

You are right. I was under a wrong impression that
__change_page_attr() always splits a large pages into 4KB pages, but I
overlooked the fact that it can handle a large page as well. So, this
approach does not work...

> I would also like a systematic way to deal with the fact
> that Xen (sigh) is stuck with a separate mapping system.
>
> I guess Linux could adopt the Xen mappings if that makes it easier, as
> long as that doesn't have a negative impact on native hardware -- we can
> possibly deal with some older chips not being optimal.

I see. I agree that supporting the PAT bit is the right direction, but
I do not know how much effort we need. I will study on this.

> However, my thinking has been to have a "reverse PAT" table in memory of memory
> types to encodings, both for regular and large pages.

I am not clear about your idea of the "reverse PAT" table. Would you
care to elaborate? How is it different from using pte_val() being a
paravirt function on Xen?

Thanks,
-Toshi




\
 
 \ /
  Last update: 2014-07-21 20:21    [W:0.067 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site