Re: [PATCH 1/1] KVM: VMX: Fix base_ptes for EPT

[Sheng Yang <sheng@linux.intel.com>]

On Wednesday 19 November 2008 18:25:32 Avi Kivity wrote:
> Sheng Yang wrote:
> > After support MTRR for EPT, memory type WB shouldn't take as default in
> > base_ptes. (Something wrong during the merging...)
>
> Yes, my fault.
>
> But don't we still have a big hole here?  The guest can set RAM to
> various attributes, even without device assignment, and create
> inconsistencies with the qemu and host kernel mapping.

The current reply from hardware guys is: the only situation that cause MCE is  
to access MMIO with cacheable memory type, and at least for EPT, they say 
using different memory type for same memory region don't have problem as far as 
we know... But for now, the hardware guys suggest to use host MTRR as the base 
for EPT memory type rather than using guest MTRR, at least it would protect us 
from MCE. And guest can operate it's PAT then promote UC to WC for performance 
and use UC for DMA. We are still in discussion to get more details now.

For now, I may try to using host MTRR for EPT as suggested.

-- 
regards
Yang, Sheng