Patchwork [BUG] : kvm_set_phys_mem: error unregistering overlapping slot: Invalid argument

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Submitter Xiao Guangrong
Date May 31, 2013, 6:51 a.m.
Message ID <51A8485A.4000605@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/247856/
State New
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Comments

Xiao Guangrong - May 31, 2013, 6:51 a.m.
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.
Jordan Justen - May 31, 2013, 7:14 a.m.
On Thu, May 30, 2013 at 11:51 PM, Xiao Guangrong
<xiaoguangrong@linux.vnet.ibm.com> wrote:
> 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.

I think that I might have found that the flash memory had an issue
with transitioning from flash to rom mode with code like this on the
3.8 kernel. I'll test it on 3.8 & 3.9.

-Jordan

> 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;
>
>
Jordan Justen - May 31, 2013, 8:01 a.m.
On Fri, May 31, 2013 at 12:14 AM, Jordan Justen <jljusten@gmail.com> wrote:
> On Thu, May 30, 2013 at 11:51 PM, Xiao Guangrong
> <xiaoguangrong@linux.vnet.ibm.com> wrote:
>> 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.
>
> I think that I might have found that the flash memory had an issue
> with transitioning from flash to rom mode with code like this on the
> 3.8 kernel. I'll test it on 3.8 & 3.9.

Yes, the issue still occurs on 3.9, and even the "double free" doesn't
work on 3.9 like it did on 3.8.

This issue is a bit of a corner case for flash, but still important. I
hope maybe Xiao might have time to help me understand it. (I'll email
Xiao off-list about this.)

But, for now, I think Xiao's patch will fix things for the non-flash
case, and will not totally break flash support either.

-Jordan
Paolo Bonzini - May 31, 2013, 8:23 a.m.
Il 31/05/2013 08:51, Xiao Guangrong ha scritto:
> 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;
> 
> 
> 
> 

Thanks, can you submit it for uq/master?  Please Cc kvm@vger.kernel.org
too, and use [PATCH uq/master] as the prefix.

Paolo

Patch

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;