Re: [PATCH for-4.5] libxl: do not load roms for any NICs except the first to avoid wasting memory

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Nov 21, 2014 at 05:11:09PM +0000, Stefano Stabellini wrote:
> The rom is used for pxebooting. We don't need to allow pxebooting from
> more than one network card.  Loading a romfile for every NIC wastes

Why not? Why can't we PXE boot from each network card?

> memory and as a matter of fact breaks configurations with more than 4
> NICs as QEMU fails to allocate memory on behalf of the guest.

What if you have four different type of NICs? Say 1 rlt8193, 1 e1000, one eepro,
and ne2k ?

Don't you want to load the ROM for each one?
> 
> With this fix, it is possible to assign more than 4 rtl8139 NICs to the
> guest.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> 
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> index 3e191c3..f907ca9 100644
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -674,9 +674,10 @@ static char ** libxl__build_device_model_args_new(libxl__gc *gc,
>                                                  LIBXL_NIC_TYPE_VIF_IOEMU);
>                  flexarray_append(dm_args, "-device");
>                  flexarray_append(dm_args,
> -                   libxl__sprintf(gc, "%s,id=nic%d,netdev=net%d,mac=%s",
> +                   libxl__sprintf(gc, "%s,id=nic%d,netdev=net%d,mac=%s%s",
>                                                  nics[i].model, nics[i].devid,
> -                                                nics[i].devid, smac));
> +                                                nics[i].devid, smac,
> +                                                i ? ",romfile=\"\"" : ""));
>                  flexarray_append(dm_args, "-netdev");
>                  flexarray_append(dm_args, GCSPRINTF(
>                                            "type=tap,id=net%d,ifname=%s,"
> 
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