KVM: unmap pages from the iommu when slots are removed
We've been adding new mappings, but not destroying old mappings.
This can lead to a page leak as pages are pinned using
get_user_pages, but only unpinned with put_page if they still
exist in the memslots list on vm shutdown. A memslot that is
destroyed while an iommu domain is enabled for the guest will
therefore result in an elevated page reference count that is
never cleared.
Additionally, without this fix, the iommu is only programmed
with the first translation for a gpa. This can result in
peer-to-peer errors if a mapping is destroyed and replaced by a
new mapping at the same gpa as the iommu will still be pointing
to the original, pinned memory address.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 665a260..72cbf08 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -596,6 +596,7 @@
#ifdef CONFIG_IOMMU_API
int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot);
+void kvm_iommu_unmap_pages(struct kvm *kvm, struct kvm_memory_slot *slot);
int kvm_iommu_map_guest(struct kvm *kvm);
int kvm_iommu_unmap_guest(struct kvm *kvm);
int kvm_assign_device(struct kvm *kvm,
@@ -609,6 +610,11 @@
return 0;
}
+static inline void kvm_iommu_unmap_pages(struct kvm *kvm,
+ struct kvm_memory_slot *slot)
+{
+}
+
static inline int kvm_iommu_map_guest(struct kvm *kvm)
{
return -ENODEV;
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index a457d21..fec1723 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -310,6 +310,11 @@
}
}
+void kvm_iommu_unmap_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ kvm_iommu_put_pages(kvm, slot->base_gfn, slot->npages);
+}
+
static int kvm_iommu_unmap_memslots(struct kvm *kvm)
{
int idx;
@@ -320,7 +325,7 @@
slots = kvm_memslots(kvm);
kvm_for_each_memslot(memslot, slots)
- kvm_iommu_put_pages(kvm, memslot->base_gfn, memslot->npages);
+ kvm_iommu_unmap_pages(kvm, memslot);
srcu_read_unlock(&kvm->srcu, idx);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 42b7393..9739b53 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -808,12 +808,13 @@
if (r)
goto out_free;
- /* map the pages in iommu page table */
+ /* map/unmap the pages in iommu page table */
if (npages) {
r = kvm_iommu_map_pages(kvm, &new);
if (r)
goto out_free;
- }
+ } else
+ kvm_iommu_unmap_pages(kvm, &old);
r = -ENOMEM;
slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots),