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Re: [Qemu-devel] FW_CFG_NB_CPUS vs fwcfg file 'etc/boot-cpus'
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] FW_CFG_NB_CPUS vs fwcfg file 'etc/boot-cpus' |
Date: |
Fri, 11 Nov 2016 16:05:59 +0100 |
On Fri, 11 Nov 2016 09:44:03 -0500
"Kevin O'Connor" <address@hidden> wrote:
> On Fri, Nov 11, 2016 at 03:36:19PM +0100, Igor Mammedov wrote:
> > On Fri, 11 Nov 2016 15:02:36 +0100
> > Laszlo Ersek <address@hidden> wrote:
> >
> > > adding Jeff Fan and Jordan Justen
> > >
> > > On 11/11/16 13:57, Igor Mammedov wrote:
> > > > While looking at OVMF and how it handles CPUs (ACPI/AP wakeup),
> > > > I've noticed that it uses legacy FW_CFG_NB_CPUS(0x05) to get
> > > > the number of present at start CPUs.
> > >
> > > Where exactly do you see this?
> > That's the only place in OVMF, but according to google there are
> > other firmwares that use FW_CFG_NB_CPUS so we are not free to remove
> > it and break guests.
> >
> > So I'd just drop not yet released 'etc/boot-cpus',
> > of cause SeaBIOS should be fixed and its blob in QEMU updated.
>
> I have no preference between FW_CFG_NB_CPUS and 'etc/boot-cpus'. Note
> that SeaBIOS v1.10 was released with the code using 'etc/boot-cpus'
> though. If it's to go away, we'll need a SeaBIOS stable branch
> release with the change.
Yep, we'd need a stable for that.
It still probably better then keeping 2 exactly same interfaces
when we have a chance to maintain only one.
Without supplier of 'etc/boot-cpus' (QEMU) it will behave like
it used before, i.e. hang with x2apic configuration.
>
> -Kevin
>