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Subject[PATCH v5 8/9] mmu: spp: Enable Lazy mode SPP protection
Date
To deal with SPP protected 4KB pages within hugepage(2MB,1GB etc),
the hugepage entry is first zapped when set subpage permission, then
in tdp_page_fault(), it checks whether the gfn should be mapped to
PT_PAGE_TABLE_LEVEL or PT_DIRECTORY_LEVEL level depending on gfn
inclusion of SPP protected page range.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/kvm/mmu.c | 14 ++++++++++++
arch/x86/kvm/vmx/spp.c | 48 ++++++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/spp.h | 4 ++++
3 files changed, 66 insertions(+)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a632c6b3c326..c9c430d2c7e3 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3240,6 +3240,17 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t gpa, int write,
map_writable);
direct_pte_prefetch(vcpu, it.sptep);
++vcpu->stat.pf_fixed;
+ if (level == PT_PAGE_TABLE_LEVEL) {
+ struct kvm_subpage sbp = {0};
+ int pages;
+
+ sbp.base_gfn = gfn;
+ sbp.npages = 1;
+ pages = kvm_spp_get_permission(vcpu->kvm, &sbp);
+ if (pages == 1 && sbp.access_map[0] != FULL_SPP_ACCESS)
+ kvm_spp_mark_protection(vcpu->kvm, &sbp);
+ }
+
return ret;
}

@@ -4183,6 +4194,9 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
if (level > PT_DIRECTORY_LEVEL &&
!check_hugepage_cache_consistency(vcpu, gfn, level))
level = PT_DIRECTORY_LEVEL;
+
+ check_spp_protection(vcpu, gfn, &force_pt_level,&level);
+
gfn &= ~(KVM_PAGES_PER_HPAGE(level) - 1);
}

diff --git a/arch/x86/kvm/vmx/spp.c b/arch/x86/kvm/vmx/spp.c
index b6fc2e313b59..7f7a3749c35b 100644
--- a/arch/x86/kvm/vmx/spp.c
+++ b/arch/x86/kvm/vmx/spp.c
@@ -547,6 +547,54 @@ inline u64 construct_spptp(unsigned long root_hpa)
}
EXPORT_SYMBOL_GPL(construct_spptp);

+bool is_spp_protected(struct kvm_memory_slot *slot, gfn_t gfn, int level)
+{
+ int page_num = KVM_PAGES_PER_HPAGE(level);
+ int i;
+ gfn &= ~(page_num - 1);
+
+ for (i = 0; i < page_num; ++i) {
+ if (*gfn_to_subpage_wp_info(slot, gfn + i) != FULL_SPP_ACCESS)
+ return true;
+ }
+ return false;
+}
+
+bool check_spp_protection(struct kvm_vcpu *vcpu, gfn_t gfn,
+ bool *force_pt_level, int *level)
+{
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_memory_slot *slot;
+ u32 access;
+
+ if (!kvm->arch.spp_active)
+ return false;
+
+ slot = gfn_to_memslot(kvm, gfn);
+
+ if (!slot)
+ return false;
+
+ if (*level == PT_PAGE_TABLE_LEVEL) {
+ access = *gfn_to_subpage_wp_info(slot, gfn);
+
+ if (access != FULL_SPP_ACCESS) {
+ *force_pt_level = true;
+ return true;
+ }
+ } else {
+ if (is_spp_protected(slot, gfn, PT_PDPE_LEVEL)) {
+ bool protected = is_spp_protected(slot, gfn,
+ PT_DIRECTORY_LEVEL);
+ *level = protected ? PT_PAGE_TABLE_LEVEL :
+ PT_DIRECTORY_LEVEL;
+ *force_pt_level = protected;
+ return true;
+ }
+ }
+ return false;
+}
+
int kvm_vm_ioctl_get_subpages(struct kvm *kvm,
struct kvm_subpage *spp_info)
{
diff --git a/arch/x86/kvm/vmx/spp.h b/arch/x86/kvm/vmx/spp.h
index 8925a6ca4d3b..ed7852bb6b33 100644
--- a/arch/x86/kvm/vmx/spp.h
+++ b/arch/x86/kvm/vmx/spp.h
@@ -4,9 +4,13 @@

#define FULL_SPP_ACCESS ((u32)((1ULL << 32) - 1))

+int kvm_spp_get_permission(struct kvm *kvm, struct kvm_subpage *spp_info);
+int kvm_spp_mark_protection(struct kvm *kvm, struct kvm_subpage *spp_info);
bool is_spp_spte(struct kvm_mmu_page *sp);
void restore_spp_bit(u64 *spte);
bool was_spp_armed(u64 spte);
+bool check_spp_protection(struct kvm_vcpu *vcpu, gfn_t gfn,
+ bool *force_pt_level, int *level);
inline u64 construct_spptp(unsigned long root_hpa);
int kvm_vm_ioctl_get_subpages(struct kvm *kvm,
struct kvm_subpage *spp_info);
--
2.17.2
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