Re: [Xen-devel] [PATCH 4 of 5] Add support for mapping grant references into HVM guests by modifying the P2M

[NAHieu <nahieu@xxxxxxxxx>]

On Tue, May 26, 2009 at 6:08 PM, Steven Smith <steven.smith@xxxxxxxxxx> wrote:
>> I understand that we are going to drop Xen 32bit, and support only Xen
>> 64bit on this feature??
> That's the plan, yes.
>
>> I believe that Xen 32bit is still important and desired by many
>> people. So please considere supporting that with your patch.
> The problem is that we only have a limited number of bits available in
> the P2M entries, which limits the number of distinct types of P2M
> entry which we can encode.  On 32-bit Xen, that limit is eight, of
> which seven are already used, and the grant mapping patch needs
> another two (one for read-write maps, and one for read-only).  There
> just isn't enough room everything we want to do.
>
> It'd be easy enough to make grant mapping work on 32-bit Xen if we
> were willing to drop some other feature (populate-on-demand, say), but
> I don't think that would be an acceptable solution.  Finding somewhere
> else to stash the required bits would significantly complicate things,
> and, since there aren't any particularly convincing use-cases yet for
> even the 64-bit variant, I didn't think that would be worthwhile.

OK, I see.

I want to try your patch. However, my Dom0 is 32bit, so Xen is 32 bit,
too (I compiled Xen from source code). How can I compile Xen in 64bit
for your patch now?

If it is not possible (or easy) to do that now, could you please
provide the patch to cross compile Xen in 64bit, too?
 That would be useful to try your patch, and also for other things.

Thanks,
N

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