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[Qemu-devel] Re: [PATCH] new parameter boot=on|off for "-net nic" and "-
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: [PATCH] new parameter boot=on|off for "-net nic" and "-device" NIC devices |
Date: |
Tue, 21 Sep 2010 16:52:36 +0200 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
On Tue, Sep 21, 2010 at 04:18:56PM +0200, Bernhard Kohl wrote:
> 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<address@hidden>
> >>> Signed-off-by: Bernhard Kohl<address@hidden>
> >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'?
Sounds good.
> >- 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?
I think so, too.
> >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
Sounds good.
--
MST