Re: [Xen-devel] [PATCH V6 4/4] x86/altp2m: fix display frozen when switching to a new view early

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 11/15/18 10:26 PM, George Dunlap wrote:
> 
> 
>> On Nov 14, 2018, at 8:40 PM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> 
>> wrote:
>>
>> When an new altp2m view is created very early on guest boot, the
>> display will freeze (although the guest will run normally). This
>> may also happen on resizing the display. The reason is the way
>> Xen currently (mis)handles logdirty VGA: it intentionally
>> misconfigures VGA pages so that they will fault.
>>
>> The problem is that it only does this in the host p2m. Once we
>> switch to a new altp2m, the misconfigured entries will no longer
>> fault, so the display will not be updated.
>>
>> This patch:
>> * updates ept_handle_misconfig() to use the active altp2m instead
>>  of the hostp2m;
>> * modifies p2m_change_entry_type_global(), p2m_memory_type_changed
>>  and p2m_change_type_range() to propagate their changes to all
>>  valid altp2ms.
>>
>> With the introduction of altp2m fields in p2m_memory_type_changed()
>> the whole function has been put under CONFIG_HVM.
> 
> Sorry — actually, I think there’s yet another issue lurking here:  
> p2m_finish_type_change(). I’ll poke around a bit more tomorrow.

OK, I'll wait for your recommendation before working on the last patch
of the series.


Thanks,
Razvan

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