Re: [PATCH v3 14/22] microvm: use 2G split unconditionally

[Paolo Bonzini]

On 27/05/20 14:25, Igor Mammedov wrote:
>>   (2) we loose a gigabyte page.
>           I'm not sure waht exactly we loose in this case.
>           Lets assume we allocating guest 5G of continuous RAM using 1G huge 
> pages,
>           in this case I'd think that on host side MMIO overlay won't affect 
> RAM blob
>           on guest side pagetables will be fragmented due to MMIO holes, but 
> guest still
>           could use huge pages smaller ones in fragmented area and 1G where 
> there is no fragmentation.

Access to the 3G-4G area would not be able to use 1G EPT pages.

But why use 2G split instead of 3G?  There's only very little MMIO and
no PCI hole (including no huge MMCONFIG BAR) on microvm.

Paolo