Re: [Xen-devel] [PATCH 5/7] x86/traps: Lift all non-entrypoint logic in entry_int82() up into C

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.05.17 at 11:27, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 04/05/17 08:27, Jan Beulich wrote:
>> As said before, I don't view it as a reasonable setup to allow only
>> 64-bit HVM guests, so unless there is an intention to have a
>> configuration where only PVH guests are supported (i.e. neither
>> PV nor traditional HVM), I don't think allowing the option to be
>> turned off makes sense on x86.
> 
> HVM and PVH aren't very different, but there will be a small amount of
> work required to get plain HVM booting like this, because of hvmloader
> currently being 32bit only.  I do see (potentially) value in allowing
> 64bit-only traditional HVM guests, e.g. with a 64bit OVMF firmware
> (although this is already turning fairly PVH in nature).

So that would then be yet another construct with no raw hardware
equivalent. I'd prefer if we strove for improving our compatibility with
raw hardware (as we do in various other places, you being one of
the primary advocates to do so) instead of inventing new custom
environments. Furthermore, while I can see the benefit of e.g. not
allowing PV guests for security reasons, I'm having a hard time
imagining some security benefit from disallowing a HVM guest to run
in 32-bit mode. But perhaps you've thought of something already...

Jan


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