From b34ff95dc36776993ebeceecba851dc3e8d3c686 Mon Sep 17 00:00:00 2001
From: Eduardo Habkost <ehabkost@redhat.com>
Date: Tue, 14 Apr 2009 14:41:58 -0300
Subject: [PATCH 4/6] 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.

(cherry picked from commit 17db0a051b269d2b1d05326c53bc4eec6d5d72b1)

[ehabkost: solved cherry-pick conflict at include/linux/kvm.h]

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1239733121-27615-1-git-send-email-ehabkost@redhat.com>
Bugzilla: 500263
RH-Upstream-status: applied(kvm/queue)
Acked-by: john cooper <john.cooper@redhat.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Acked-by: Avi Kivity <avi@redhat.com>
---
 include/linux/kvm.h |    2 ++
 virt/kvm/kvm_main.c |    3 ++-
 2 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index f9f9f8a..89baafb 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -404,6 +404,8 @@ struct kvm_trace_rec {
 #define KVM_CAP_REINJECT_CONTROL 24
 #endif
 #define KVM_CAP_IRQ_INJECT_STATUS 26
+/* Another bug in KVM_SET_USER_MEMORY_REGION fixed: */
+#define KVM_CAP_JOIN_MEMORY_REGIONS_WORKS 30
 
 /*
  * ioctls for VM fds
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b24aa5e..19140f7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -996,7 +996,7 @@ 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)))
@@ -2005,6 +2005,7 @@ static long kvm_dev_ioctl_check_extension_generic(long arg)
 	switch (arg) {
 	case KVM_CAP_USER_MEMORY:
 	case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
+	case KVM_CAP_JOIN_MEMORY_REGIONS_WORKS:
 		return 1;
 	default:
 		break;
-- 
1.6.3.rc4.29.g8146