lkml.org 
[lkml]   [2010]   [Dec]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
DateWed, 22 Dec 2010 10:02:58 -0500
FromKonrad Rzeszutek Wilk <>
SubjectRe: [PATCH 04/10] xen/mmu: For 1-1 mapping, automatically set _PAGE_IOMAP.
On Tue, Dec 21, 2010 at 02:29:31PM -0800, Jeremy Fitzhardinge wrote:
> On 12/21/2010 01:37 PM, Konrad Rzeszutek Wilk wrote:
> > This means that for PFNs (specifically: those in any E820 gaps
> > or non-RAM E820 regions) that have 1-1 mapping we set the
> > _PAGE_IOMAP flag.
> >
> > Later on we could remove the _PAGE_IOMAP code handling, but
> > for right now lets keep this in to not introduce any bisection
> > failures across this patchset.
> >
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > ---
> > arch/x86/xen/mmu.c | 3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> > index 4ba7e4e..bd02e7d 100644
> > --- a/arch/x86/xen/mmu.c
> > +++ b/arch/x86/xen/mmu.c
> > @@ -832,6 +832,9 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
> > pteval_t flags = val & PTE_FLAGS_MASK;
> > unsigned long mfn = pfn_to_mfn(pfn);
> >
> > + if (mfn == pfn)
> > + flags |= _PAGE_IOMAP;
>
> Why? Does it really make sense to set _PAGE_IOMAP if they just happen
> to be the same value?

Yes. Without this, user applications, such as 'dmidecode' cannot get
data.

But I think with ditching a bunch of the _PAGE_IOMAP in the xen/mmu.c we can
remove this.

I would rather keep this patch as temporary scaffolding and when the
other set of patches is ready for the _PAGE_IOMAP, ditch this one.

>
> J


\
 
 \ /
  Last update: 2010-12-22 16:07    [from the cache]
©2003-2010