[patch 04/10] KVM: MMU: mode specific sync_page

[Marcelo Tosatti <mtosatti@redhat.com>]

[-- Attachment #1: kvm-oos-sync-page --]
[-- Type: text/plain, Size: 4393 bytes --]

Examine guest pagetable and bring the shadow back in sync. Caller is responsible
for local TLB flush before re-entering guest mode.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm/arch/x86/kvm/mmu.c
===================================================================
--- kvm.orig/arch/x86/kvm/mmu.c
+++ kvm/arch/x86/kvm/mmu.c
@@ -871,6 +871,12 @@ static void nonpaging_prefetch_page(stru
 		sp->spt[i] = shadow_trap_nonpresent_pte;
 }
 
+static int nonpaging_sync_page(struct kvm_vcpu *vcpu,
+			       struct kvm_mmu_page *sp)
+{
+	return 1;
+}
+
 static struct kvm_mmu_page *kvm_mmu_lookup_page(struct kvm *kvm, gfn_t gfn)
 {
 	unsigned index;
@@ -1548,6 +1554,7 @@ static int nonpaging_init_context(struct
 	context->gva_to_gpa = nonpaging_gva_to_gpa;
 	context->free = nonpaging_free;
 	context->prefetch_page = nonpaging_prefetch_page;
+	context->sync_page = nonpaging_sync_page;
 	context->root_level = 0;
 	context->shadow_root_level = PT32E_ROOT_LEVEL;
 	context->root_hpa = INVALID_PAGE;
@@ -1595,6 +1602,7 @@ static int paging64_init_context_common(
 	context->page_fault = paging64_page_fault;
 	context->gva_to_gpa = paging64_gva_to_gpa;
 	context->prefetch_page = paging64_prefetch_page;
+	context->sync_page = paging64_sync_page;
 	context->free = paging_free;
 	context->root_level = level;
 	context->shadow_root_level = level;
@@ -1616,6 +1624,7 @@ static int paging32_init_context(struct 
 	context->gva_to_gpa = paging32_gva_to_gpa;
 	context->free = paging_free;
 	context->prefetch_page = paging32_prefetch_page;
+	context->sync_page = paging32_sync_page;
 	context->root_level = PT32_ROOT_LEVEL;
 	context->shadow_root_level = PT32E_ROOT_LEVEL;
 	context->root_hpa = INVALID_PAGE;
@@ -1635,6 +1644,7 @@ static int init_kvm_tdp_mmu(struct kvm_v
 	context->page_fault = tdp_page_fault;
 	context->free = nonpaging_free;
 	context->prefetch_page = nonpaging_prefetch_page;
+	context->sync_page = nonpaging_sync_page;
 	context->shadow_root_level = kvm_x86_ops->get_tdp_level();
 	context->root_hpa = INVALID_PAGE;
 
Index: kvm/arch/x86/kvm/paging_tmpl.h
===================================================================
--- kvm.orig/arch/x86/kvm/paging_tmpl.h
+++ kvm/arch/x86/kvm/paging_tmpl.h
@@ -503,6 +503,61 @@ static void FNAME(prefetch_page)(struct 
 	}
 }
 
+/*
+ * Using the cached information from sp->gfns is safe because:
+ * - The spte has a reference to the struct page, so the pfn for a given gfn
+ *   can't change unless all sptes pointing to it are nuked first.
+ * - Alias changes zap the entire shadow cache.
+ */
+static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
+{
+	int i, offset, nr_present;
+
+	offset = nr_present = 0;
+
+	if (PTTYPE == 32)
+		offset = sp->role.quadrant << PT64_LEVEL_BITS;
+
+	for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
+		if (is_shadow_present_pte(sp->spt[i])) {
+			unsigned pte_access;
+			pt_element_t gpte;
+			gpa_t pte_gpa;
+			gfn_t gfn = sp->gfns[i];
+
+			pte_gpa = gfn_to_gpa(sp->gfn);
+			pte_gpa += (i+offset) * sizeof(pt_element_t);
+
+			if (kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte,
+						  sizeof(pt_element_t)))
+				return -EINVAL;
+
+			if (gpte_to_gfn(gpte) != gfn || !(gpte & PT_ACCESSED_MASK)) {
+				rmap_remove(vcpu->kvm, &sp->spt[i]);
+				if (is_present_pte(gpte))
+					sp->spt[i] = shadow_trap_nonpresent_pte;
+				else
+					sp->spt[i] = shadow_notrap_nonpresent_pte;
+				continue;
+			}
+
+			if (!is_present_pte(gpte)) {
+				rmap_remove(vcpu->kvm, &sp->spt[i]);
+				sp->spt[i] = shadow_notrap_nonpresent_pte;
+				continue;
+			}
+
+			nr_present++;
+			pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
+			set_spte(vcpu, &sp->spt[i], pte_access, 0, 0,
+				 is_dirty_pte(gpte), 0, gfn,
+				 spte_to_pfn(sp->spt[i]), true);
+		}
+	}
+
+	return !nr_present;
+}
+
 #undef pt_element_t
 #undef guest_walker
 #undef shadow_walker
Index: kvm/include/asm-x86/kvm_host.h
===================================================================
--- kvm.orig/include/asm-x86/kvm_host.h
+++ kvm/include/asm-x86/kvm_host.h
@@ -220,6 +220,8 @@ struct kvm_mmu {
 	gpa_t (*gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t gva);
 	void (*prefetch_page)(struct kvm_vcpu *vcpu,
 			      struct kvm_mmu_page *page);
+	int (*sync_page)(struct kvm_vcpu *vcpu,
+			 struct kvm_mmu_page *sp);
 	hpa_t root_hpa;
 	int root_level;
 	int shadow_root_level;

--