Re: [PATCH v2] x86/kvm: Force legacy PCI hole to UC when overriding MTRRs for TDX/SNP

[Sean Christopherson]

On Thu, Aug 28, 2025, Binbin Wu wrote:
> > Note #2, relying on guest firmware to handle this scenario, e.g. by setting
> > virtual MTRRs and then consuming them in Linux, is not a viable option, as
> > the virtual MTRR state is managed by the untrusted hypervisor, and because
> > OVMF at least has stopped programming virtual MTRRs when running as a TDX
> > guest.
> 
> Not sure if it needs to mention that with this option, Linux kernel will set
> CR0.CD=1 when programming MTRRs, which will trigger unexpected #VE in TDX guest.

I don't think it's worth bringing up, because that is a very solvable problem,
and orthogonal to the issues with using the untrusted hypervisor to store/track
the virtual MTRR values.