Re: [PATCH v19 016/130] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX

Isaku Yamahata
2024-03-06T22:22:35Z

On Wed, Mar 06, 2024 at 03:13:22PM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

>
>
> On 2/26/2024 4:25 PM, isaku.yamahata@intel.com wrote:
> > From: Sean Christopherson <sean.j.christopherson@intel.com>
> >
> > Introduce a helper to directly (pun intended) fault-in a TDP page
> > without having to go through the full page fault path. This allows
> > TDX to get the resulting pfn and also allows the RET_PF_* enums to
> > stay in mmu.c where they belong.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > ---
> > v19:
> > - Move up for KVM_MEMORY_MAPPING.
> > - Add goal_level for the caller to know how many pages are mapped.
> >
> > v14 -> v15:
> > - Remove loop in kvm_mmu_map_tdp_page() and return error code based on
> > RET_FP_xxx value to avoid potential infinite loop. The caller should
> > loop on -EAGAIN instead now.
> >
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > ---
> > arch/x86/kvm/mmu.h | 3 +++
> > arch/x86/kvm/mmu/mmu.c | 58 ++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 61 insertions(+)
> >
> > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> > index 60f21bb4c27b..d96c93a25b3b 100644
> > --- a/arch/x86/kvm/mmu.h
> > +++ b/arch/x86/kvm/mmu.h
> > @@ -183,6 +183,9 @@ static inline void kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu,
> > __kvm_mmu_refresh_passthrough_bits(vcpu, mmu);
> > }
> > +int kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
> > + u8 max_level, u8 *goal_level);
> > +
> > /*
> > * Check if a given access (described through the I/D, W/R and U/S bits of a
> > * page fault error code pfec) causes a permission fault with the given PTE
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 61674d6b17aa..ca0c91f14063 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -4615,6 +4615,64 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> > return direct_page_fault(vcpu, fault);
> > }
> > +int kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code,
> > + u8 max_level, u8 *goal_level)
> > +{
> > + int r;
> > + struct kvm_page_fault fault = (struct kvm_page_fault) {
> > + .addr = gpa,
> > + .error_code = error_code,
> > + .exec = error_code & PFERR_FETCH_MASK,
> > + .write = error_code & PFERR_WRITE_MASK,
> > + .present = error_code & PFERR_PRESENT_MASK,
> > + .rsvd = error_code & PFERR_RSVD_MASK,
> > + .user = error_code & PFERR_USER_MASK,
> > + .prefetch = false,
> > + .is_tdp = true,
> > + .is_private = error_code & PFERR_GUEST_ENC_MASK,
> > + .nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(vcpu->kvm),
> > + };
> > +
> > + WARN_ON_ONCE(!vcpu->arch.mmu->root_role.direct);
> > + fault.slot = kvm_vcpu_gfn_to_memslot(vcpu, fault.gfn);
> > +
> > + r = mmu_topup_memory_caches(vcpu, false);
>
> Does it need a cache topup here?
> Both kvm_tdp_mmu_page_fault() and direct_page_fault() will call
> mmu_topup_memory_caches() when needed.

You're right. As the called function has changed, I missed to remove it.
--
Isaku Yamahata <isaku.yamahata@linux.intel.com>