On Fri, Jul 25, 2025, Sean Christopherson wrote:
> On Thu, Jul 24, 2025, Ackerley Tng wrote:
> I also don't want to effectively speculatively add kvm_gmem_mapping_order() or
> expand kvm_gmem_get_pfn(), e.g. to say "no create", so what if we just do this?
>
> /* For faults, use the gmem information that was resolved earlier. */
> if (fault) {
> pfn = fault->pfn;
> max_level = fault->max_level;
> } else {
> /* TODO: Call into guest_memfd once hugepages are supported. */
Aha! Even better, we can full on WARN:
WARN_ONCE(1, "Get pfn+order from guest_memfd");
Because guest_memfd doesn't yet support dirty logging:
/* Dirty logging private memory is not currently supported. */
if (mem->flags & KVM_MEM_GUEST_MEMFD)
valid_flags &= ~KVM_MEM_LOG_DIRTY_PAGES;
which kills off the kvm_mmu_recover_huge_pages() call from kvm_mmu_slot_apply_flags().
And if KVM ever supports in-place recover for kvm_recover_nx_huge_pages() (which
is doubtful given that mitigation shouldn't be required going forward), lack of
hugepage support means any guest_memfd-based shadow page can't be a possible NX
hugepage.
