From 374cbac0333ddf5cf1c6637efaf7f3adcc67fd75 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Fri, 5 Jan 2007 16:36:43 -0800 Subject: [PATCH] [PATCH] KVM: MMU: Write protect guest pages when a shadow is created for them When we cache a guest page table into a shadow page table, we need to prevent further access to that page by the guest, as that would render the cache incoherent. Signed-off-by: Avi Kivity Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/kvm/mmu.c | 72 +++++++++++++++++++++++++++++---------- drivers/kvm/paging_tmpl.h | 1 + 2 files changed, 55 insertions(+), 18 deletions(-) diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c index 47c699c21c..ba813f49f8 100644 --- a/drivers/kvm/mmu.c +++ b/drivers/kvm/mmu.c @@ -274,6 +274,35 @@ static void rmap_remove(struct kvm *kvm, u64 *spte) } } +static void rmap_write_protect(struct kvm *kvm, u64 gfn) +{ + struct page *page; + struct kvm_memory_slot *slot; + struct kvm_rmap_desc *desc; + u64 *spte; + + slot = gfn_to_memslot(kvm, gfn); + BUG_ON(!slot); + page = gfn_to_page(slot, gfn); + + while (page->private) { + if (!(page->private & 1)) + spte = (u64 *)page->private; + else { + desc = (struct kvm_rmap_desc *)(page->private & ~1ul); + spte = desc->shadow_ptes[0]; + } + BUG_ON(!spte); + BUG_ON((*spte & PT64_BASE_ADDR_MASK) != + page_to_pfn(page) << PAGE_SHIFT); + BUG_ON(!(*spte & PT_PRESENT_MASK)); + BUG_ON(!(*spte & PT_WRITABLE_MASK)); + rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte); + rmap_remove(kvm, spte); + *spte &= ~(u64)PT_WRITABLE_MASK; + } +} + static void kvm_mmu_free_page(struct kvm_vcpu *vcpu, hpa_t page_hpa) { struct kvm_mmu_page *page_head = page_header(page_hpa); @@ -444,6 +473,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, page->gfn = gfn; page->role = role; hlist_add_head(&page->hash_link, bucket); + if (!metaphysical) + rmap_write_protect(vcpu->kvm, gfn); return page; } @@ -705,6 +736,7 @@ static void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu) static void paging_new_cr3(struct kvm_vcpu *vcpu) { + pgprintk("%s: cr3 %lx\n", __FUNCTION__, vcpu->cr3); mmu_free_roots(vcpu); mmu_alloc_roots(vcpu); kvm_mmu_flush_tlb(vcpu); @@ -727,24 +759,11 @@ static inline void set_pte_common(struct kvm_vcpu *vcpu, *shadow_pte |= access_bits << PT_SHADOW_BITS_OFFSET; if (!dirty) access_bits &= ~PT_WRITABLE_MASK; - if (access_bits & PT_WRITABLE_MASK) { - struct kvm_mmu_page *shadow; - shadow = kvm_mmu_lookup_page(vcpu, gaddr >> PAGE_SHIFT); - if (shadow) - pgprintk("%s: found shadow page for %lx, marking ro\n", - __FUNCTION__, (gfn_t)(gaddr >> PAGE_SHIFT)); - if (shadow) - access_bits &= ~PT_WRITABLE_MASK; - } - - if (access_bits & PT_WRITABLE_MASK) - mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT); + paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK); *shadow_pte |= access_bits; - paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK); - if (!(*shadow_pte & PT_GLOBAL_MASK)) mark_pagetable_nonglobal(shadow_pte); @@ -752,11 +771,28 @@ static inline void set_pte_common(struct kvm_vcpu *vcpu, *shadow_pte |= gaddr; *shadow_pte |= PT_SHADOW_IO_MARK; *shadow_pte &= ~PT_PRESENT_MASK; - } else { - *shadow_pte |= paddr; - page_header_update_slot(vcpu->kvm, shadow_pte, gaddr); - rmap_add(vcpu->kvm, shadow_pte); + return; } + + *shadow_pte |= paddr; + + if (access_bits & PT_WRITABLE_MASK) { + struct kvm_mmu_page *shadow; + + shadow = kvm_mmu_lookup_page(vcpu, gaddr >> PAGE_SHIFT); + if (shadow) { + pgprintk("%s: found shadow page for %lx, marking ro\n", + __FUNCTION__, (gfn_t)(gaddr >> PAGE_SHIFT)); + access_bits &= ~PT_WRITABLE_MASK; + *shadow_pte &= ~PT_WRITABLE_MASK; + } + } + + if (access_bits & PT_WRITABLE_MASK) + mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT); + + page_header_update_slot(vcpu->kvm, shadow_pte, gaddr); + rmap_add(vcpu->kvm, shadow_pte); } static void inject_page_fault(struct kvm_vcpu *vcpu, diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h index f7cce443ca..cd71973c78 100644 --- a/drivers/kvm/paging_tmpl.h +++ b/drivers/kvm/paging_tmpl.h @@ -133,6 +133,7 @@ static void FNAME(walk_addr)(struct guest_walker *walker, walker->level - 1, table_gfn); } walker->ptep = ptep; + pgprintk("%s: pte %llx\n", __FUNCTION__, (u64)*ptep); } static void FNAME(release_walker)(struct guest_walker *walker) -- 2.39.5