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:
> 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.  Does FreeBSD not have a flag to 
mmap from high memory?  What is the the original problem?

Regards,

Anthony Liguori

> Index: qemu/vl.c
> @@ -9850,15 +9850,15 @@
>          phys_ram_size += ram_size;
>      }
>  
> +    /* init the dynamic translator */
> +    cpu_exec_init_all(tb_size * 1024 * 1024);
> +
>      phys_ram_base = qemu_vmalloc(phys_ram_size);
>      if (!phys_ram_base) {
>          fprintf(stderr, "Could not allocate physical memory\n");
>          exit(1);
>      }
>  
> -    /* init the dynamic translator */
> -    cpu_exec_init_all(tb_size * 1024 * 1024);
> -
>      bdrv_init(emulate_aio);
>  
>      /* we always create the cdrom drive, even if no disk is there */
>
> Signed-off-by: Juergen Lock <nox@jelal.kn-bremen.de>
>
>
>