Re: [Qemu-devel] [BUG]: kvm_set_phys_mem: error unregistering overlapping slot: Invalid argument

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

On 05/31/2013 12:50 AM, Jordan Justen wrote:
> On Thu, May 30, 2013 at 9:08 AM, Luiz Capitulino <lcapitulino@redhat.com> wrote:
>> On Thu, 30 May 2013 18:03:04 +0200
>> Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>>> Il 30/05/2013 17:46, Luiz Capitulino ha scritto:
>>>> The culprit is commit:
>>>>
>>>> commit 235e8982ad393e5611cb892df54881c872eea9e1
>>>> Author: Jordan Justen <jordan.l.justen@intel.com>
>>>> Date:   Wed May 29 01:27:26 2013 -0700
>>>>
>>>>     kvm: support using KVM_MEM_READONLY flag for regions
>>>>
>>>> I'm running 3.9.2-200.fc18, btw. And, error checking is missing on the
>>>> first call to kvm_vm_ioctl().
> 
> As noted in the code, the first call is for KVM commit 75d61fbc.
> 
> I'm not sure we want to fail if an error occurs when making that call.
> (I'm pretty sure we don't want to in fact.)
> 
> Xiao, any thoughts?

I have reproduced this bug, it seems that the bug is caused by double free
the memslot. After these change, it can boot the guest now.

diff --git a/kvm-all.c b/kvm-all.c
index 8e7bbf8..405480e 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -206,7 +206,8 @@ static int kvm_set_user_memory_region(KVMState *s, KVMSlot *slot)
     if (s->migration_log) {
         mem.flags |= KVM_MEM_LOG_DIRTY_PAGES;
     }
-    if (mem.flags & KVM_MEM_READONLY) {
+
+    if (slot->memory_size && mem.flags & KVM_MEM_READONLY) {
         /* Set the slot size to 0 before setting the slot to the desired
          * value. This is needed based on KVM commit 75d61fbc. */
         mem.memory_size = 0;