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Re: hypercalls with 64-bit results

  • To: Anthony PERARD <anthony.perard@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Thu, 17 Jun 2021 17:09:03 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
  • Delivery-date: Thu, 17 Jun 2021 15:09:15 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 17.06.2021 17:03, Anthony PERARD wrote:
> On Thu, Jun 17, 2021 at 10:03:50AM +0200, Jan Beulich wrote:
>> But it's not just XENMEM_maximum_gpfn that's affected; that's just the
>> one pointing out the underlying issue. Plus if so, shouldn't we avoid
>> returning values that are going to be truncated (and, as can be seen
>> here, then get perhaps recognized as error codes up the call chain)?
>>> For now, I'd agree with trying to undo the change in OVMF.
>> Anthony, thoughts?
> I can map the shared_info page somewhere else, that fine. The hard part
> is figuring out where. I can probably map it just after the guest RAM
> (as described by the e820 from hvmloader or Xen).

Can't you put it (not necessarily immediately) next to the LAPIC
page, for example? Or the IO-APIC one? Or somewhere in that area,
which normally OSes won't use for placing BARs?




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