lkml.org 
[lkml]   [2008]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: issue with patch "x86: no CPA on iounmap"
Siddha, Suresh B wrote:
> This is wrt to x86 git commit f56d005d30342a45d8af2b75ecccc82200f09600
> "x86: no CPA on iounmap"
>
> This can use performance issue. When a GART driver unmaps a RAM page,
> which was mapped as UC, this commit will still retain UC attribute
> on the kernel identity mapping. This can cause mysterious performance issue
> if this freed page gets used by kernel later.
>
> For now we should change the attribute during iounmap and in future PAT
> infrastructure will have necessary hooks to avoid the aliasing issues.
>

this is a hard one; because the flipside is someone ioremapping the same page twice
(which is not impossible if there's 2 1k bars)... and then one of them gets iounmapped,
which would turn the page cachable again.


\
 
 \ /
  Last update: 2008-02-05 05:47    [from the cache]
©2003-2011 Jasper Spaans