[PATCH 07/55] KVM: Unmap kernel-allocated memory on slot destruction

From: Izik Eidus <[email protected]>

kvm_vm_ioctl_set_memory_region() is able to remove memory in addition to
adding it.  Therefore when using kernel swapping support for old userspaces,
we need to munmap the memory if the user request to remove it

Signed-off-by: Izik Eidus <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>
---
 drivers/kvm/kvm.h      |    1 +
 drivers/kvm/kvm_main.c |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index f7181a4..12de42c 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -353,6 +353,7 @@ struct kvm_memory_slot {
 	unsigned long *rmap;
 	unsigned long *dirty_bitmap;
 	unsigned long userspace_addr;
+	int user_alloc;
 };
 
 struct kvm {
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 005f2d5..0e8f77d 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -713,6 +713,7 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 
 		memset(new.rmap, 0, npages * sizeof(*new.rmap));
 
+		new.user_alloc = user_alloc;
 		if (user_alloc)
 			new.userspace_addr = mem->userspace_addr;
 		else {
@@ -727,6 +728,19 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 			if (IS_ERR((void *)new.userspace_addr))
 				goto out_unlock;
 		}
+	} else {
+		if (!old.user_alloc && old.rmap) {
+			int ret;
+
+			down_write(&current->mm->mmap_sem);
+			ret = do_munmap(current->mm, old.userspace_addr,
+					old.npages * PAGE_SIZE);
+			up_write(&current->mm->mmap_sem);
+			if (ret < 0)
+				printk(KERN_WARNING
+				       "kvm_vm_ioctl_set_memory_region: "
+				       "failed to munmap memory\n");
+		}
 	}
 
 	/* Allocate page dirty bitmap if needed */
-- 
1.5.3.7

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---

• References:
  • [PATCH 00/55] KVM patch queue review for 2.6.25 merge window (part II)
    • From: Avi Kivity <[email protected]>

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