[Qemu-devel] Re: [PATCH] new parameter boot=on|off for "-net nic" and "-device" NIC devices

[Bernhard Kohl <bernhard.kohl@nsn.com>]

Am 19.09.2010 18:07, schrieb ext Michael S. Tsirkin:
> On Tue, Sep 14, 2010 at 05:46:55PM +0200, Bernhard Kohl wrote:
>    
>> >  This patch was motivated by the following use case: In our system
>> >  the VMs usually have 4 NICs, any combination of virtio-net-pci and
>> >  pci-assign NIC devices. The VMs boot via gPXE preferably over the
>> >  pci-assign devices.
>> >  
>> >  There is no way to make this working with a combination of the
>> >  current options -net -pcidevice -device -optionrom -boot.
>> >  
>> >  With the parameter boot=off it is possible to avoid loading
>> >  and using gPXE option ROMs either for old style "-net nic" or
>> >  for "-device" NIC devices. So we can select which NIC is used
>> >  for booting.
>> >  
>> >  A side effect of the boot=off parameter is that unneeded ROMs
>> >  which might waste memory are not longer loaded. E.g. if you have
>> >  2 virtio-net-pci and 2 pci-assign NICs in sum 4 option ROMs are
>> >  loaded and the virtio ROMs take precedence over the pci-assign
>> >  ROMs. The BIOS uses the first gPXE ROM which it finds and only
>> >  needs one of them even if there are more NICs of the same type.
>> >  
>> >  Without using the boot=on|off parameter the current behaviour
>> >  does not change.
>> >  
>> >  Signed-off-by: Thomas Ostler<thomas.ostler@nsn.com>
>> >  Signed-off-by: Bernhard Kohl<bernhard.kohl@nsn.com>
>>      
> I think this is useful, however:
>
> - We have bit properties which handle parsing on/off
>    and other formats automatically. Please don't use string.
> - boot is not a great property name for PCI: what
>    you actually do is disable option rom.
>    So maybe call it 'rom' or something like that?
>    
Our main goal is to select a certain NIC's option rom for booting.
So the other roms are not needed and not loaded. We used 'boot'
as the property name as it is similar as in the '-drive' option to
select a certain disk for booting. What's about to call it 'bootrom'?
> - given you have added a property, it can now
>    be changed with -device. and visible in -device ?
>    This also has an advantage of only applying to pci devices
>    (-net option would appear to apply to non-pci but have no effect).
>    Please do not add more flag parsing in qdemu-options, net and vl.c
>    
I think it is OK that we don't support this new feature for the old
style '-net' option and only implement it for qdev / -device?
> To summarize, just add a qdev bit option and check
> the bit.
>
>    
In general, we will rework the patch and use all new qdev features.
There are also some memory leaks as Chris told us, because of the
usage of strdup.

This rework might take 2 weeks because of vacation.

Thanks
Bernhard