Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers

[Blue Swirl]

On Fri, Sep 2, 2011 at 6:49 AM, Paolo Bonzini <address@hidden> wrote:
> On 09/02/2011 02:08 AM, David Gibson wrote:
>>>
>>> >
>>>>
>>>> >  >Signed-off-by: Alexey Kardashevskiy<address@hidden>
>>>> >  >Signed-off-by: David Gibson<address@hidden>
>>>
>>> >
>>> >  It will most definitely break OpenBSD, but anyway:
>>
>> Uh, why?
>
> They use an ancient compiler because they do not want to use GPLv3.  I
> thought it was 4.1.something but actually it is 4.2.1, so it should work.

It works:

$ cat >sync_synch.c
void f(void)
{
  __sync_synchronize();
}
$ gcc -c sync_synch.c -Wall
$ objdump -d sync_synch.o

sync_synch.o:     file format elf64-sparc

Disassembly of section .text:

0000000000000000 <f>:
   0:   9d e3 bf 40     save  %sp, -192, %sp
   4:   81 43 e0 0f     membar  #StoreStore|#LoadStore|#StoreLoad|#LoadLoad
   8:   81 cf e0 08     rett  %i7 + 8
   c:   01 00 00 00     nop
$ gcc -v
Reading specs from
/usr/bin/../lib/gcc-lib/sparc64-unknown-openbsd4.9/4.2.1/specs
Target: sparc64-unknown-openbsd4.9
Configured with: OpenBSD/sparc64 system compiler
Thread model: posix
gcc version 4.2.1 20070719