KVM: Fix overlapping check for memory slots

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 and advertise this via a
KVM_CAP_JOIN_MEMORY_REGIONS_WORKS.

Cc: stable@kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 311a073afe8a..8cc137911b34 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -409,6 +409,8 @@ struct kvm_trace_rec {
 #ifdef __KVM_HAVE_DEVICE_ASSIGNMENT
 #define KVM_CAP_DEVICE_DEASSIGNMENT 27
 #endif
+/* Another bug in KVM_SET_USER_MEMORY_REGION fixed: */
+#define KVM_CAP_JOIN_MEMORY_REGIONS_WORKS 30
 
 #ifdef KVM_CAP_IRQ_ROUTING