Re: [Xen-devel] [RFC PATCH 3/3] Implement 3-level event channel routines.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.01.13 at 18:33, Wei Liu <Wei.Liu2@xxxxxxxxxx> wrote:
> On Thu, 2013-01-03 at 11:35 +0000, Jan Beulich wrote:
>> >>> On 31.12.12 at 19:22, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
>> >
>> > +static void __unmap_l2_sel(struct vcpu *v)
>> > +{
>> > +    unsigned long mfn;
>> > +
>> > +    if ( v->evtchn_pending_sel_l2 != 0 )
>> > +    {
>> > +        unmap_domain_page_global(v->evtchn_pending_sel_l2);
>> > +        mfn = virt_to_mfn(v->evtchn_pending_sel_l2);
>> 
>> virt_to_mfn() is not valid on the output of
>> map_domain_page{,_global}() (same further down). Yes, there is
>> at least one example of this in the existing code, but that's wrong
>> too, and is getting eliminated by the 16Tb patch series I'm in the
>> process of putting together.
>> 
> 
> So what's the correct way to do this? Do I need to wait for your patch
> series?

Considering that the old 32-bit case of map_domain_page()
doesn't matter anymore, using domain_page_map_to_mfn()
here would be the way to go (while the 32-bit version of it
didn't allow map_domain_page_global() to be handled through
it, my 64-bit implementation of it will).

And of course there's the obvious alternative of storing the
MFN rather than re-obtaining it in the teardown path.

Jan


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