Re: [Xen-devel] [PATCH] x86/pv: Drop create_pae_xen_mappings()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.08.17 at 10:52, <george.dunlap@xxxxxxxxxx> wrote:
> On 08/24/2017 09:40 AM, Jan Beulich wrote:
>>>>> On 23.08.17 at 20:11, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> This is leftovers from the 32bit hypervisor days.  The only Xen content in
>>> this virtual range for 32bit PV guests is the compat M2P.  It is not 
>>> critical
>>> that the mapping is present, nor is it critical that the slot is unshared.
>> 
>> Hmm, while technically correct this would allow 32-bit guests to
>> run on newer hypervisors that would fail on older ones. I'm not
>> sure this is a good idea, but I'm also not entirely opposed to it.
> 
> I think I'm missing something; why would some 32-bit guests fail on
> hypervisors which still had this mapping (which is what I presume you
> mean by "older hypervisors")?

Oh, I'm sorry - I mean a guest not playing by the rules being enforced
here, i.e. e.g. one leaving the 3rd slot empty. Testing such a guest
on an up-to-date hypervisor would not turn up any issues, yet it
would fail once run on an older one.

Jan


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