KVM: x86/mmu: Check for host MMIO exclusion from mem encrypt iff necessary
When determining whether or not a SPTE needs to have SME/SEV's memory
encryption flag set, do the moderately expensive host MMIO pfn check if
and only if the memory encryption mask is non-zero.
Note, KVM could further optimize the host MMIO checks by making a single
call to kvm_is_mmio_pfn(), but the tdp_enabled path (for EPT's memtype
handling) will likely be split out to a separate flow[*]. At that point,
a better approach would be to shove the call to kvm_is_mmio_pfn() into
VMX code so that AMD+NPT without SME doesn't get hit with an unnecessary
lookup.
[*] https://lkml.kernel.org/r/
20220321224358.1305530-3-bgardon@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <
20220415004909.2216670-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>