Re: [Qemu-devel] [PATCH] Allocate translation buffer before guest RAM, in case guest RAM is too large on 64 bit hosts

[Anthony Liguori <anthony@codemonkey.ws>]

Juergen Lock wrote:
> In article <48FDE6BA.4070102@codemonkey.ws> you write:
>   
>> Juergen Lock wrote:
>>     
>>> Hi!
>>>
>>>  The following patch appears to fix -m >= 1024 on recent FreeBSD/amd64 hosts
>>> (RELENG_7/HEAD) that no longer return high addresses for allocations by
>>> default (which was the original reason for r5331.)  As this makes sense
>>> in any case when you pass something like -m 4096 on hosts that allocate
>>> from low addresses by default (there would be no room left for the
>>> translation buffer in the low vm where it needs to be), I patched it like
>>> this instead of conditionalizing the mmap hack from r5331 on the FreeBSD
>>> version.
>>>   
>>>       
>> I fear there is too much magic here.
>>     
>
> Heh.
>
>   
>>  Does FreeBSD not have a flag to 
>> mmap from high memory?
>>     
>
>  I don't think so.
>
>   
>>  What is the the original problem?
>>
>>     
>  code_gen_buffer needs to be in the lower 4G (because of branches with
> 32 bit offsets etc.)
>   

Can you resubmit the patch with a big comment explaining why the 
allocation order is important?

Regards,

Anthony Liguori

>> Regards,
>>
>> Anthony Liguori
>>     
>
>  Thanx,
> 	Juergen
>