Re: [Xen-ia64-devel] RFC: ptc.ga implementation for SMP-g

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Mardi 04 Avril 2006 10:18, Tristan Gingold a écrit :
> Le Lundi 03 Avril 2006 20:01, Alex Williamson a écrit :
> > On Mon, 2006-04-03 at 14:38 +0100, Tristan Gingold wrote:
> > > Hi,
> > >
> > > after the comments, here is my updated patch for ptc.ga
> > > Please comment it.
> > >
> > > With this patch, the page_flags are always written atomically.  Ptc
> > > only clear it.  This eliminates itc and ptc conflicts.
> > >
> > > The other conflict is use.  This is within ia64_page_fault, between
> > > vcpu_translate and vcpu_itc_no_srlz.  This part of code is protected by
> > > a flag + counter: At entry the flag is set and the counter increment,
> > > at exit the flag is reset.  Ptc.ga waits if the flag is set and retries
> > > if the counter has changes.
> >
> > Hi Tristan,
> >
> >    Is there any way a nested page fault could double increment tlb_inuse
> > (ie. where you might hit that BUG_ON)?
>
> I don't think so.  If a fault occurs within vcpu_translate, it is a xen
> fault which won't result in calling ia64_page_fault.  vcpu_translate reads
> domain memory (guest VHPT entry), but in case of failure it doesn't inject
> a fault.
Euh, I was wrong.  In case of failure it recurses at first.

Tristan.



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