Re: [PATCH 5/8] KVM: x86/mmu: bootstrap support for Intel MBEC

[Paolo Bonzini]

On 12/23/25 06:47, Jon Kohler wrote:
> Extend kvm_mmu_page_role access bitfield from 3 to 4, where the 4th bit
> will be used to track user executable pages with Intel mode-based
> execute control (MBEC).
>
> Extend SPTE generation and introduce shadow_ux value to account for
> user and kernel executable distinctions under MBEC.

While MBEC has a different definition of the bits, GMET is essentially 
SMEP (except that AMD couldn't retrofit it into hCR4.SMEP due to how NPT 
handles the U bit).  I wonder if it's possible to handle MBEC as SMEP as 
well, with some additional handling of the SPTEs (with shadox_x_mask and 
shadow_ux_mask taking the functionality of shadow_nx_mask and 
shadow_u_mask) but no large changes to the MMU.

This should be a much simpler patch set if it can be made to work.  I'll 
take a look.

Paolo