KVM: unmap pages from the iommu when slots are removed

commit 32f6daad4651a748a58a3ab6da0611862175722f upstream.

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>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d5262319997806bb6f1fdfcfb50b6cef37428b0e..35410ef9cf6987b48dcb8f247aa29d9db84312c8 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -562,6 +562,7 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id);
 
 #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,
@@ -575,6 +576,11 @@ static inline int kvm_iommu_map_pages(struct kvm *kvm,
        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 a195c07fa8290b44cb435f5ac06d841507e33503..fd817a2cb2404b6b584eb60ea746f1cfe712dda8 100644 (file)
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -309,6 +309,11 @@ static void kvm_iommu_put_pages(struct kvm *kvm,
        }
 }
 
+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 i, idx;
@@ -317,10 +322,9 @@ static int kvm_iommu_unmap_memslots(struct kvm *kvm)
        idx = srcu_read_lock(&kvm->srcu);
        slots = kvm_memslots(kvm);
 
-       for (i = 0; i < slots->nmemslots; i++) {
-               kvm_iommu_put_pages(kvm, slots->memslots[i].base_gfn,
-                                   slots->memslots[i].npages);
-       }
+       for (i = 0; i < slots->nmemslots; i++)
+               kvm_iommu_unmap_pages(kvm, &slots->memslots[i]);
+
        srcu_read_unlock(&kvm->srcu, idx);
 
        return 0;

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d9cfb782cb81a87fc5ef4f1734df1a308a55539b..e401c1b118e96a7d594c64b21547cd4fb9cfd0cb 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -802,12 +802,13 @@ skip_lpage:
        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 = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);