On Wed, Nov 19, 2008 at 12:51:00PM -0600, Anthony Liguori wrote:
>
> But the problem still exists even with this code. I checked.
>
> So if you have something working without modifying the kernel, can you
> post it?
>
> Regards,
>
> Anthony Liguori
Ok, how do you feel about this one?
My proposal is to always delete a memslot before reusing the space,
but controlling this behaviour by a flag, so we can maintain backwards
compatibility with people using older versions of the interface.
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index f18b86f..66ee286 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -39,6 +39,7 @@ struct kvm_userspace_memory_region {
/* for kvm_memory_region::flags */
#define KVM_MEM_LOG_DIRTY_PAGES 1UL
+#define KVM_MEM_FREE_BEFORE_ALLOC 2UL
/* for KVM_IRQ_LINE */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4c39d4f..41f5666 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -735,24 +735,31 @@ int __kvm_set_memory_region(struct kvm *kvm,
base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
npages = mem->memory_size >> PAGE_SHIFT;
- if (!npages)
- mem->flags &= ~KVM_MEM_LOG_DIRTY_PAGES;
+
+ r = kvm_check_overlap(kvm, base_gfn, npages, memslot);
+ if (r)
+ goto out_free;
+
new = old = *memslot;
- new.base_gfn = base_gfn;
- new.npages = npages;
- new.flags = mem->flags;
+ if (!npages)
+ mem->flags &= ~KVM_MEM_LOG_DIRTY_PAGES;
- /* Disallow changing a memory slot's size. */
- r = -EINVAL;
- if (npages && old.npages && npages != old.npages)
- goto out_free;
- r = kvm_check_overlap(kvm, base_gfn, npages, memslot);
- if (r)
+ if (mem->flags & KVM_MEM_FREE_BEFORE_ALLOC)
+ kvm_free_physmem_slot(&new, NULL);
+
+ else {
+ /* Disallow changing a memory slot's size. */
+ r = -EINVAL;
+ if (npages && old.npages && npages != old.npages)
goto out_free;
+ }
+ new.base_gfn = base_gfn;
+ new.flags = mem->flags;
+ new.npages = npages;
/* Free page dirty bitmap if unneeded */
if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES))
@@ -771,6 +778,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
memset(new.rmap, 0, npages * sizeof(*new.rmap));
new.user_alloc = user_alloc;
+ /*
+ * hva_to_rmmap() serialzies with the mmu_lock and to be
+ * safe it has to ignore memslots with !user_alloc &&
+ * !userspace_addr.
+ */
+ if (user_alloc)
+ new.userspace_addr = mem->userspace_addr;
+ else
+ new.userspace_addr = 0;
}
if (npages && !new.lpage_info) {
int largepages = npages / KVM_PAGES_PER_HPAGE;
@@ -791,15 +807,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
if ((base_gfn+npages) % KVM_PAGES_PER_HPAGE)
new.lpage_info[largepages-1].write_count = 1;
}
- /*
- * hva_to_rmmap() serialzies with the mmu_lock and to be
- * safe it has to ignore memslots with !user_alloc &&
- * !userspace_addr.
- */
- if (npages && user_alloc)
- new.userspace_addr = mem->userspace_addr;
- else
- new.userspace_addr = 0;
/* Allocate page dirty bitmap if needed */
if ((new.flags & KVM_MEM_LOG_DIRTY_PAGES) && !new.dirty_bitmap) {
@@ -830,7 +837,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
goto out_free;
}
- kvm_free_physmem_slot(&old, &new);
+
+ if (!(mem->flags & KVM_MEM_FREE_BEFORE_ALLOC))
+ kvm_free_physmem_slot(&old, &new);
#ifdef CONFIG_DMAR
/* map the pages in iommu page table */
r = kvm_iommu_map_pages(kvm, base_gfn, npages);
@@ -840,7 +849,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
return 0;
out_free:
- kvm_free_physmem_slot(&new, &old);
+
+ if (!(mem->flags & KVM_MEM_FREE_BEFORE_ALLOC))
+ kvm_free_physmem_slot(&new, &old);
out:
return r;
