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authorTakuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>2013-01-30 14:40:41 +0400
committerMarcelo Tosatti <mtosatti@redhat.com>2013-02-05 04:56:47 +0400
commit75d61fbcf563373696578570e914f555e12c8d97 (patch)
tree8835d8a5cf79704569f568675792672c930746ae /virt
parentf64c0398939483eb1d8951f24fbc21e94ed54457 (diff)
downloadlinux-75d61fbcf563373696578570e914f555e12c8d97.tar.xz
KVM: set_memory_region: Disallow changing read-only attribute later
As Xiao pointed out, there are a few problems with it: - kvm_arch_commit_memory_region() write protects the memory slot only for GET_DIRTY_LOG when modifying the flags. - FNAME(sync_page) uses the old spte value to set a new one without checking KVM_MEM_READONLY flag. Since we flush all shadow pages when creating a new slot, the simplest fix is to disallow such problematic flag changes: this is safe because no one is doing such things. Reviewed-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Cc: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c35
1 files changed, 12 insertions, 23 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 64c5dc37c6a1..2e93630b4add 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -754,7 +754,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
struct kvm_memory_slot *slot;
struct kvm_memory_slot old, new;
struct kvm_memslots *slots = NULL, *old_memslots;
- bool old_iommu_mapped;
enum kvm_mr_change change;
r = check_memory_region_flags(mem);
@@ -797,15 +796,14 @@ int __kvm_set_memory_region(struct kvm *kvm,
new.npages = npages;
new.flags = mem->flags;
- old_iommu_mapped = old.npages;
-
r = -EINVAL;
if (npages) {
if (!old.npages)
change = KVM_MR_CREATE;
else { /* Modify an existing slot. */
if ((mem->userspace_addr != old.userspace_addr) ||
- (npages != old.npages))
+ (npages != old.npages) ||
+ ((new.flags ^ old.flags) & KVM_MEM_READONLY))
goto out;
if (base_gfn != old.base_gfn)
@@ -867,7 +865,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
/* slot was deleted or moved, clear iommu mapping */
kvm_iommu_unmap_pages(kvm, &old);
- old_iommu_mapped = false;
/* From this point no new shadow pages pointing to a deleted,
* or moved, memslot will be created.
*
@@ -898,25 +895,17 @@ int __kvm_set_memory_region(struct kvm *kvm,
/*
* IOMMU mapping: New slots need to be mapped. Old slots need to be
- * un-mapped and re-mapped if their base changes or if flags that the
- * iommu cares about change (read-only). Base change unmapping is
- * handled above with slot deletion, so we only unmap incompatible
- * flags here. Anything else the iommu might care about for existing
- * slots (size changes, userspace addr changes) is disallowed above,
- * so any other attribute changes getting here can be skipped.
+ * un-mapped and re-mapped if their base changes. Since base change
+ * unmapping is handled above with slot deletion, mapping alone is
+ * needed here. Anything else the iommu might care about for existing
+ * slots (size changes, userspace addr changes and read-only flag
+ * changes) is disallowed above, so any other attribute changes getting
+ * here can be skipped.
*/
- if (change != KVM_MR_DELETE) {
- if (old_iommu_mapped &&
- ((new.flags ^ old.flags) & KVM_MEM_READONLY)) {
- kvm_iommu_unmap_pages(kvm, &old);
- old_iommu_mapped = false;
- }
-
- if (!old_iommu_mapped) {
- r = kvm_iommu_map_pages(kvm, &new);
- if (r)
- goto out_slots;
- }
+ if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
+ r = kvm_iommu_map_pages(kvm, &new);
+ if (r)
+ goto out_slots;
}
/* actual memory is freed via old in kvm_free_physmem_slot below */