Re: [PATCH v6 01/16] KVM: TDP_MMU: Go to next level if smaller private mapping exists

Isaku Yamahata
2023-11-17T01:05:27Z

On Thu, Nov 16, 2023 at 09:32:22AM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

>
>
> On 11/7/2023 11:00 PM, isaku.yamahata@intel.com wrote:
> > From: Xiaoyao Li <xiaoyao.li@intel.com>
> >
> > Cannot map a private page as large page if any smaller mapping exists.
> >
> > It has to wait for all the not-mapped smaller page to be mapped and
> > promote it to larger mapping.
> >
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > ---
> > arch/x86/kvm/mmu/tdp_mmu.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> > index 2c5257628881..d806574f7f2d 100644
> > --- a/arch/x86/kvm/mmu/tdp_mmu.c
> > +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> > @@ -1287,7 +1287,8 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> > tdp_mmu_for_each_pte(iter, mmu, is_private, raw_gfn, raw_gfn + 1) {
> > int r;
> > - if (fault->nx_huge_page_workaround_enabled)
> > + if (fault->nx_huge_page_workaround_enabled ||
> > + kvm_gfn_shared_mask(vcpu->kvm))
> As I mentioned in https://lore.kernel.org/kvm/fef75d54-e319-5170-5f76-f5abc4856315@linux.intel.com/,
> The change of this patch will not take effect.
> If "fault->nx_huge_page_workaround_enabled" is false, the condition
> "spte_to_child_sp(spte)->nx_huge_page_disallowed" will not be true.
>
> IIUC, the function disallowed_hugepage_adjust() currently is only to handle
> nx_huge_page_workaround, it seems no special handling needed for TD.
> > disallowed_hugepage_adjust(fault, iter.old_spte, iter.level);
> > /*

You're correct. Now guest memfd memory attributes takes care of large page
mapping, this patch is uncessary. Will drop this patch.
--
Isaku Yamahata <isaku.yamahata@linux.intel.com>