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

[Juergen Lock]

In article <address@hidden> 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.)

>Regards,
>
>Anthony Liguori

 Thanx,
        Juergen