Re: [PATCH v3 3/9] KVM: x86: MMU: Rename get_cr3() --> get_pgd() and clear high bits for pgd

[Sean Christopherson <seanjc@google.com>]

On Fri, Dec 09, 2022, Robert Hoo wrote:
> The get_cr3() is the implementation of kvm_mmu::get_guest_pgd(), well, CR3
> cannot be naturally equivalent to pgd, SDM says CR3 high bits are reserved,
> must be zero.
> And now, with LAM feature's introduction, bit 61 ~ 62 are used.
> So, rename get_cr3() --> get_pgd() to better indicate function purpose and
> in it, filtered out CR3 high bits.

Depends on one's interpreation of "PGD".  KVM says it's the full thing, e.g. the
nEPT hook returns the full EPTP, not EP4TA (or EP5TA).  I don't think stripping
bits in get_cr3() is the right approach, e.g. the user might want the full thing
for comparison.  E.g. the PCID bits are left as is.

Changing get_cr3() but not nested_svm_get_tdp_cr3() and nested_ept_get_eptp() is
also weird.

I think my preference would be to strip the LAM bits in the few places that want
the physical address and keep get_cr3() as is.