[Qemu-devel] [PATCH] kvm: Fix overlapping check for memory slots

[Jan Kiszka <jan.kiszka@web.de>]

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This nice little buglet complicates a smarter slot management in qemu
user space just "slightly". Sigh...

-------->

When checking for overlapping slots on registration of a new one, kvm
currently also considers zero-length (ie. deleted) slots and rejects
requests incorrectly. This finally denies user space from joining slots.
Fix the check by skipping deleted slots.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

 virt/kvm/kvm_main.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 363af32..18f06d2 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1117,7 +1117,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
 		struct kvm_memory_slot *s = &kvm->memslots[i];
 
-		if (s == memslot)
+		if (s == memslot || !s->npages)
 			continue;
 		if (!((base_gfn + npages <= s->base_gfn) ||
 		      (base_gfn >= s->base_gfn + s->npages)))


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