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Re: [PATCH] stubdom: foreignmemory: Fix build after 0dbb4be739c5

  • To: Julien Grall <julien@xxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 13 Jul 2021 16:23:14 +0200
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  • Cc: Julien Grall <jgrall@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Costin Lupu <costin.lupu@xxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>
  • Delivery-date: Tue, 13 Jul 2021 14:23:26 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 13.07.2021 16:19, Julien Grall wrote:
> On 13/07/2021 15:14, Jan Beulich wrote:
>>> And I don't think it should be named XC_PAGE_*, but rather XEN_PAGE_*.
>> Even that doesn't seem right to me, at least in principle. There shouldn't
>> be a build time setting when it may vary at runtime. IOW on Arm I think a
>> runtime query to the hypervisor would be needed instead.
> Yes, we want to be able to use the same userspace/OS without rebuilding 
> to a specific hypervisor page size.
>> And thinking
>> even more generally, perhaps there could also be mixed (base) page sizes
>> in use at run time, so it may need to be a bit mask which gets returned.
> I am not sure to understand this. Are you saying the hypervisor may use 
> at the same time different page size?

I think so, yes. And I further think the hypervisor could even allow its
guests to do so. There would be a distinction between the granularity at
which RAM gets allocated and the granularity at which page mappings (RAM
or other) can be established. Which yields an environment which I'd say
has no clear "system page size".




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