KVM: MMU: Make gfn_to_page() always safe

[linux-block.git] / drivers / kvm / kvm_main.c

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 1879b409bed2fc4e3e23b02ecefdb3c883bc207c..47000be25479f4030245ceea5b08d8a51765db0f 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -993,6 +993,12 @@ static int kvm_vm_ioctl_set_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
        return r;
 }
 
+int is_error_page(struct page *page)
+{
+       return page == bad_page;
+}
+EXPORT_SYMBOL_GPL(is_error_page);
+
 gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
 {
        int i;
@@ -1034,7 +1040,7 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
        gfn = unalias_gfn(kvm, gfn);
        slot = __gfn_to_memslot(kvm, gfn);
        if (!slot)
-               return NULL;
+               return bad_page;
        return slot->phys_mem[gfn - slot->base_gfn];
 }
 EXPORT_SYMBOL_GPL(gfn_to_page);
@@ -1054,7 +1060,7 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
        struct page *page;
 
        page = gfn_to_page(kvm, gfn);
-       if (!page)
+       if (is_error_page(page))
                return -EFAULT;
        page_virt = kmap_atomic(page, KM_USER0);
 
@@ -1092,7 +1098,7 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
        struct page *page;
 
        page = gfn_to_page(kvm, gfn);
-       if (!page)
+       if (is_error_page(page))
                return -EFAULT;
        page_virt = kmap_atomic(page, KM_USER0);
 
@@ -1130,7 +1136,7 @@ int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)
        struct page *page;
 
        page = gfn_to_page(kvm, gfn);
-       if (!page)
+       if (is_error_page(page))
                return -EFAULT;
        page_virt = kmap_atomic(page, KM_USER0);
 
@@ -3068,7 +3074,7 @@ static struct page *kvm_vm_nopage(struct vm_area_struct *vma,
 
        pgoff = ((address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
        page = gfn_to_page(kvm, pgoff);
-       if (!page)
+       if (is_error_page(page))
                return NOPAGE_SIGBUS;
        get_page(page);
        if (type != NULL)
@@ -3383,7 +3389,7 @@ static struct sys_device kvm_sysdev = {
        .cls = &kvm_sysdev_class,
 };
 
-hpa_t bad_page_address;
+struct page *bad_page;
 
 static inline
 struct kvm_vcpu *preempt_notifier_to_vcpu(struct preempt_notifier *pn)
@@ -3512,7 +3518,6 @@ EXPORT_SYMBOL_GPL(kvm_exit_x86);
 
 static __init int kvm_init(void)
 {
-       static struct page *bad_page;
        int r;
 
        r = kvm_mmu_module_init();
@@ -3523,16 +3528,13 @@ static __init int kvm_init(void)
 
        kvm_arch_init();
 
-       bad_page = alloc_page(GFP_KERNEL);
+       bad_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 
        if (bad_page == NULL) {
                r = -ENOMEM;
                goto out;
        }
 
-       bad_page_address = page_to_pfn(bad_page) << PAGE_SHIFT;
-       memset(__va(bad_page_address), 0, PAGE_SIZE);
-
        return 0;
 
 out:
@@ -3545,7 +3547,7 @@ out4:
 static __exit void kvm_exit(void)
 {
        kvm_exit_debug();
-       __free_page(pfn_to_page(bad_page_address >> PAGE_SHIFT));
+       __free_page(bad_page);
        kvm_mmu_module_exit();
 }