At 16:41 +0000 on 21 Jan (1295628107), George Dunlap wrote:
> Tim / Xiaoyun, do you think something like this might work?
Worth a try. I don't think it will do much harm -- there should be no
cases where dom0 really must map a dying domain's memory.
Tim.
> On Fri, Jan 21, 2011 at 4:32 PM, George Dunlap <dunlapg@xxxxxxxxx> wrote:
> > [sorry, accidentally sent too early]
> >
> > On Fri, Jan 21, 2011 at 4:29 PM, George Dunlap <dunlapg@xxxxxxxxx> wrote:
> >> I'm not sure the exact rationale behind the "cannot fail" flag; but it
> >> looks like in grant_table.c, both callers of gfn_to_mfn_unshare()
> >> handle the case where the returned p2m entry is just
> >
> > ...invalid. I wonder if "unsharing" the page, but marking the entry
> > invalid during death would help.
> >
> > I suppose the problem there is that if you're keeping the VM around
> > but paused for analysis, you'll have holes in your address space. But
> > just returning an invalid entry to the callers who try to unshare
> > pages might work.
> >
> > -George
> >
> diff -r 9ca9331c9780 xen/include/asm-x86/p2m.h
> --- a/xen/include/asm-x86/p2m.h Fri Jan 21 15:37:36 2011 +0000
> +++ b/xen/include/asm-x86/p2m.h Fri Jan 21 16:41:58 2011 +0000
> @@ -390,7 +390,14 @@
> must_succeed
> ? MEM_SHARING_MUST_SUCCEED : 0) )
> {
> - BUG_ON(must_succeed);
> + if ( must_succeed
> + && p2m->domain->is_dying )
> + {
> + mfn = INVALID_MFN;
> + *p2mt=p2m_invalid;
> + }
> + else
> + BUG_ON(must_succeed);
> return mfn;
> }
> mfn = gfn_to_mfn(p2m, gfn, p2mt);
--
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd. (Company #02937203, SL9 0BG)
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