Re: [Xen-devel] [V1 PATCH] PVH: avoid call to handle_mmio

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.06.14 at 21:42, <mukesh.rathor@xxxxxxxxxx> wrote:
> On Thu, 05 Jun 2014 07:28:30 +0100
> "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
>> The fundamentally wrong thing is that real hardware wouldn't
>> surface #GP on any wrong physical address - with one exception,
>> the only possibility would be #MC, and I don't think this would
>> ever happen for truly unpopulated ranges. (The exception being
>> on AMD, where #PF gets surfaced when trying to access a page
>> referring to the HT reserved address range.) IOW even on HVM
>> it is wrong for us to inject #GP in cases like this.
> 
> We, internally here, discussed the idea of injecting #PF instead of #GP. 
> That 
> makes sense from baremetal perspective. IOW, if we look at it from the 
> prespective that the guest kernel put a bad pte entry, then on baremetal
> it will get a #PF.

This very much depends on what's wrong with the PTE - reserved
bits being set would yield #PF, but an out-of-(valid-)range physical
address wouldn't normally. And it's that which we've been discussing
here.

Jan


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