[Qemu-devel] Re: [PATCH] Fix segfault with ram_size > 4095M without kvm

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 12/08/2010 12:27 PM, Luiz Capitulino wrote:
> On Wed, 08 Dec 2010 12:23:12 -0600
> Anthony Liguori<aliguori@linux.vnet.ibm.com>  wrote:
>
>    
>> On 12/08/2010 12:01 PM, Luiz Capitulino wrote:
>>      
>>> Currently, x86_64-softmmu qemu segfaults when trying to use>   4095M memsize.
>>> This patch adds a simple check and error message (much like the 2047 limit on
>>> 32-bit hosts) on ram_size in the control path after we determine we're
>>> not using kvm
>>>
>>> Upstream qemu-kvm is affected if using the -no-kvm option; this patch address
>>> the segfault there as well.
>>>
>>> Signed-off-by: Ryan Harper<ryanh@us.ibm.com>
>>> Signed-off-by: Aurelien Jarno<aurelien@aurel32.net>
>>> ---
>>> NOTE: this patch was applied in the v0.12.x branch, but it seems it got
>>>         lost for master
>>>
>>>        
>> No, it was intentional.  We should fix the segv, this is not a known
>> limitation but rather a bug.
>>      
> A TCG bug, I presume?
>    

Dunno, that's why we shouldn't just paper over it.

Regards,

Anthony Liguori

>    
>> Regards,
>>
>> Anthony Liguori
>>
>>      
>>>    vl.c |    6 ++++++
>>>    1 files changed, 6 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/vl.c b/vl.c
>>> index 2dbb6db..bb9c21c 100644
>>> --- a/vl.c
>>> +++ b/vl.c
>>> @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp)
>>>                fprintf(stderr, "failed to initialize KVM\n");
>>>                exit(1);
>>>            }
>>> +    } else {
>>> +        /* without kvm enabled, we can only support 4095 MB RAM */
>>> +        if (ram_size>   (4095UL<<   20)) {
>>> +            fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n");
>>> +            exit(1);
>>> +        }
>>>        }
>>>
>>>        if (qemu_init_main_loop()) {
>>>
>>>        
>>      
>