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authorSean Christopherson <sean.j.christopherson@intel.com>2020-02-18 13:07:28 -0800
committerPaolo Bonzini <pbonzini@redhat.com>2020-03-16 17:57:23 +0100
commit163da372dec52183a4f6142c302716b939ec5df5 (patch)
tree545dcde22a42b9f735837f833b3a9bba4e4a271b /virt
parente96c81ee89d80e1a0fe50a0e9be40c1b77e14aaa (diff)
downloadlinux-163da372dec52183a4f6142c302716b939ec5df5.tar.gz
KVM: Clean up local variable usage in __kvm_set_memory_region()
Clean up __kvm_set_memory_region() to achieve several goals: - Remove local variables that serve no real purpose - Improve the readability of the code - Better show the relationship between the 'old' and 'new' memslot - Prepare for dynamically sizing memslots - Document subtle gotchas (via comments) Note, using 'tmp' to hold the initial memslot is not strictly necessary at this juncture, e.g. 'old' could be directly copied from id_to_memslot(), but keep the pointer usage as id_to_memslot() will be able to return a NULL pointer once memslots are dynamically sized. Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c50
1 files changed, 26 insertions, 24 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 642215e2aeb2..1632e466ad6f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1071,13 +1071,11 @@ static int kvm_delete_memslot(struct kvm *kvm,
int __kvm_set_memory_region(struct kvm *kvm,
const struct kvm_userspace_memory_region *mem)
{
- int r;
- gfn_t base_gfn;
- unsigned long npages;
- struct kvm_memory_slot *slot;
struct kvm_memory_slot old, new;
- int as_id, id;
+ struct kvm_memory_slot *tmp;
enum kvm_mr_change change;
+ int as_id, id;
+ int r;
r = check_memory_region_flags(mem);
if (r)
@@ -1102,54 +1100,58 @@ int __kvm_set_memory_region(struct kvm *kvm,
if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
return -EINVAL;
- slot = id_to_memslot(__kvm_memslots(kvm, as_id), id);
- base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
- npages = mem->memory_size >> PAGE_SHIFT;
-
- if (npages > KVM_MEM_MAX_NR_PAGES)
- return -EINVAL;
-
/*
* Make a full copy of the old memslot, the pointer will become stale
* when the memslots are re-sorted by update_memslots(), and the old
* memslot needs to be referenced after calling update_memslots(), e.g.
- * to free its resources and for arch specific behavior.
+ * to free its resources and for arch specific behavior. Kill @tmp
+ * after making a copy to deter potentially dangerous usage.
*/
- old = *slot;
+ tmp = id_to_memslot(__kvm_memslots(kvm, as_id), id);
+ old = *tmp;
+ tmp = NULL;
+
if (!mem->memory_size)
return kvm_delete_memslot(kvm, mem, &old, as_id);
- new = old;
-
new.id = id;
- new.base_gfn = base_gfn;
- new.npages = npages;
+ new.base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
+ new.npages = mem->memory_size >> PAGE_SHIFT;
new.flags = mem->flags;
new.userspace_addr = mem->userspace_addr;
+ if (new.npages > KVM_MEM_MAX_NR_PAGES)
+ return -EINVAL;
+
if (!old.npages) {
change = KVM_MR_CREATE;
+ new.dirty_bitmap = NULL;
+ memset(&new.arch, 0, sizeof(new.arch));
} else { /* Modify an existing slot. */
if ((new.userspace_addr != old.userspace_addr) ||
- (npages != old.npages) ||
+ (new.npages != old.npages) ||
((new.flags ^ old.flags) & KVM_MEM_READONLY))
return -EINVAL;
- if (base_gfn != old.base_gfn)
+ if (new.base_gfn != old.base_gfn)
change = KVM_MR_MOVE;
else if (new.flags != old.flags)
change = KVM_MR_FLAGS_ONLY;
else /* Nothing to change. */
return 0;
+
+ /* Copy dirty_bitmap and arch from the current memslot. */
+ new.dirty_bitmap = old.dirty_bitmap;
+ memcpy(&new.arch, &old.arch, sizeof(new.arch));
}
if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
/* Check for overlaps */
- kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) {
- if (slot->id == id)
+ kvm_for_each_memslot(tmp, __kvm_memslots(kvm, as_id)) {
+ if (tmp->id == id)
continue;
- if (!((base_gfn + npages <= slot->base_gfn) ||
- (base_gfn >= slot->base_gfn + slot->npages)))
+ if (!((new.base_gfn + new.npages <= tmp->base_gfn) ||
+ (new.base_gfn >= tmp->base_gfn + tmp->npages)))
return -EEXIST;
}
}