| Message ID | 9151e79d4f5af888242b9589c0a106a49a97837c.1655761627.git.ashish.kalra@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) | expand |
On Mon, Jun 20, 2022 at 4:09 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote: > > From: Brijesh Singh <brijesh.singh@amd.com> > > The SEV-SNP VMs may call the page state change VMGEXIT to add the GPA > as private or shared in the RMP table. The page state change VMGEXIT > will contain the RMP page level to be used in the RMP entry. If the > page level between the TDP and RMP does not match then, it will result > in nested-page-fault (RMP violation). > > The SEV-SNP VMGEXIT handler will use the kvm_mmu_get_tdp_walk() to get > the current page-level in the TDP for the given GPA and calculate a > workable page level. If a GPA is mapped as a 4K-page in the TDP, but > the guest requested to add the GPA as a 2M in the RMP entry then the > 2M request will be broken into 4K-pages to keep the RMP and TDP > page-levels in sync. > > TDP SPTEs are RCU protected so need to put kvm_mmu_get_tdp_walk() in RCU > read-side critical section by using walk_shadow_page_lockless_begin() and > walk_lockless_shadow_page_lockless_end(). This fixes the > "suspicious RCU usage" message seen with lockdep kernel build. > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > Signed-off by: Ashish Kalra <ashish.kalra@amd.com> > --- > arch/x86/kvm/mmu.h | 2 ++ > arch/x86/kvm/mmu/mmu.c | 33 +++++++++++++++++++++++++++++++++ > 2 files changed, 35 insertions(+) > > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h > index c99b15e97a0a..d55b5166389a 100644 > --- a/arch/x86/kvm/mmu.h > +++ b/arch/x86/kvm/mmu.h > @@ -178,6 +178,8 @@ static inline bool is_nx_huge_page_enabled(void) > return READ_ONCE(nx_huge_pages); > } > > +bool kvm_mmu_get_tdp_walk(struct kvm_vcpu *vcpu, gpa_t gpa, kvm_pfn_t *pfn, int *level); > + > static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > u32 err, bool prefetch) > { > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 569021af349a..c1ac486e096e 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4151,6 +4151,39 @@ kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa, > } > EXPORT_SYMBOL_GPL(kvm_mmu_map_tdp_page); > > +bool kvm_mmu_get_tdp_walk(struct kvm_vcpu *vcpu, gpa_t gpa, kvm_pfn_t *pfn, int *level) > +{ > + u64 sptes[PT64_ROOT_MAX_LEVEL + 1]; > + int leaf, root; > + > + walk_shadow_page_lockless_begin(vcpu); > + > + if (is_tdp_mmu(vcpu->arch.mmu)) > + leaf = kvm_tdp_mmu_get_walk(vcpu, gpa, sptes, &root); > + else > + leaf = get_walk(vcpu, gpa, sptes, &root); > + > + walk_shadow_page_lockless_end(vcpu); > + > + if (unlikely(leaf < 0)) > + return false; > + > + /* Check if the leaf SPTE is present */ > + if (!is_shadow_present_pte(sptes[leaf])) > + return false; > + > + *pfn = spte_to_pfn(sptes[leaf]); > + if (leaf > PG_LEVEL_4K) { > + u64 page_mask = KVM_PAGES_PER_HPAGE(leaf) - KVM_PAGES_PER_HPAGE(leaf - 1); > + *pfn |= (gpa_to_gfn(gpa) & page_mask); Similar to the discussion in the other patch, I believe you should apply the same fix here as well. It should be u64 page_mask = KVM_PAGES_PER_HPAGE(leaf) - 1; > + } > + > + *level = leaf; > + > + return true; > +} > +EXPORT_SYMBOL_GPL(kvm_mmu_get_tdp_walk); > + > static void nonpaging_init_context(struct kvm_mmu *context) > { > context->page_fault = nonpaging_page_fault; > -- > 2.25.1 >
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index c99b15e97a0a..d55b5166389a 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -178,6 +178,8 @@ static inline bool is_nx_huge_page_enabled(void) return READ_ONCE(nx_huge_pages); } +bool kvm_mmu_get_tdp_walk(struct kvm_vcpu *vcpu, gpa_t gpa, kvm_pfn_t *pfn, int *level); + static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u32 err, bool prefetch) { diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 569021af349a..c1ac486e096e 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4151,6 +4151,39 @@ kvm_pfn_t kvm_mmu_map_tdp_page(struct kvm_vcpu *vcpu, gpa_t gpa, } EXPORT_SYMBOL_GPL(kvm_mmu_map_tdp_page); +bool kvm_mmu_get_tdp_walk(struct kvm_vcpu *vcpu, gpa_t gpa, kvm_pfn_t *pfn, int *level) +{ + u64 sptes[PT64_ROOT_MAX_LEVEL + 1]; + int leaf, root; + + walk_shadow_page_lockless_begin(vcpu); + + if (is_tdp_mmu(vcpu->arch.mmu)) + leaf = kvm_tdp_mmu_get_walk(vcpu, gpa, sptes, &root); + else + leaf = get_walk(vcpu, gpa, sptes, &root); + + walk_shadow_page_lockless_end(vcpu); + + if (unlikely(leaf < 0)) + return false; + + /* Check if the leaf SPTE is present */ + if (!is_shadow_present_pte(sptes[leaf])) + return false; + + *pfn = spte_to_pfn(sptes[leaf]); + if (leaf > PG_LEVEL_4K) { + u64 page_mask = KVM_PAGES_PER_HPAGE(leaf) - KVM_PAGES_PER_HPAGE(leaf - 1); + *pfn |= (gpa_to_gfn(gpa) & page_mask); + } + + *level = leaf; + + return true; +} +EXPORT_SYMBOL_GPL(kvm_mmu_get_tdp_walk); + static void nonpaging_init_context(struct kvm_mmu *context) { context->page_fault = nonpaging_page_fault;