Re: [Xen-devel] [PATCH v2 09/12] x86/altp2m: add remaining support routines.

[Ed White <edmund.h.white@xxxxxxxxx>]

On 06/24/2015 07:44 PM, Lengyel, Tamas wrote:
>> +    if ( altp2m_active )
>> +    {
>> +        if ( altp2mhvm_hap_nested_page_fault(v, gpa, gla, npfec, &p2m) ==
>> 1 )
>> +        {
>> +            /* entry was lazily copied from host -- retry */
>>
> 
> So I'm not fully following this logic here. I can see that the altp2m entry
> got copied from the host. Why is there a need for the retry, why not just
> continue?

At this point the EPT's that the hardware is using have been made valid
by software, but the hardware has already failed the access so you have
to restart the operation. This isn't in any way specific to altp2m,
it's how page fault logic works generally.

Ed


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