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RE: [Xen-devel] Review needed for "commonisation" ofcommon/grant_table.c

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, <cwc22@xxxxxxxxx>
Subject: RE: [Xen-devel] Review needed for "commonisation" ofcommon/grant_table.c
From: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
Date: Mon, 13 Jun 2005 07:23:51 -0700
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Thread-topic: [Xen-devel] Review needed for "commonisation" ofcommon/grant_table.c
> >It means that on x86, there are a number of error conditions due
> >to the way page tables are handled, but none (or perhaps different
> >error conditions) apply on ia64.  The checks for the page table
> >issues are x86 specific and would need to be macro-ized somehow
> >for the code to be portable.
> Yes. So can I suggest splitting grant table into common part and
> arch-dep part? Though not looking into detail code of grant table yet,
> there should be many places operating on page table which should be.
> That would be better than adding arch definition in common part. :)
> Other page table related stuff has already been pulled into
> arch-dependent directories (majorly meaning mm.c).

It appears to me that it probably won't be necessary to split the code
into common and arch-dep as the differences can be abstracted
by macros and static inlines in header files.  However, if
the macros create difficulty for x86, either splitting the
code -- or perhaps including an asm/grant_table.h -- would
be OK with me.  What do you think Christopher?

> We need reference counts on ia64, not for special page, but 
> page share.
> Front end driver and VBD needs to share pages that domA owns to domB
> where backend is running. Also shared info frame will be 
> shared between
> domain and xen, where reference count is also necessary. We'll send a
> patch to you after grabbing it from our local tree cleanly. :)

I'm still not clear on the value of reference counts for Xen/ia64
since unprivileged domains do not have direct access to physical
memory.  Since this is an arch-dep discussion, let's switch this
discussion to xen-ia64-devel.


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