[Xen-devel] Re: [PATCHEs]: support more than 32 VCPUs in guests

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

 On 06/15/2010 11:45 AM, Mukesh Rathor wrote:
> On Tue, 15 Jun 2010 09:30:35 +0100
> Jeremy Fitzhardinge<jeremy@xxxxxxxx>  wrote:
>
> > On 06/15/2010 03:49 AM, Mukesh Rathor wrote:
> > > On Mon, 14 Jun 2010 10:37:30 +0100
> > > Jeremy Fitzhardinge<jeremy@xxxxxxxx>  wrote:
> > >
> > >
> > > > On 06/10/2010 03:13 AM, Mukesh Rathor wrote:
> > > >
> > > > > Well, BUG_ON is only triggered if booting more than 32 VCPUs on a
> > > > > *very old* xen (pre xen 3.1.0).
> > > > >
> > > > > Looking at code closely, we could just set setup_max_cpus to 32
> > > > > some where in xen function, perhaps even in xen_vcpu_setup().
> > > > > That way later in smp_init() it would just be ok.
> > > > Yes.
> > > >
> > > >
> > > > > One thing tho, the per cpus areas are already setup at that point,
> > > > > so that would need to be cleaned. BTW, I don't understand why
> > > > > have_vcpu_info_placement is set to 0 in xen_guest_init()?
> > > > xen_guest_init is used by the pvhvm path, and hvm domains don't
> > > > have a notion of vcpu info placement.
> > > >
> > > >
> > > > > What minimum version of xen is required to run pvops kernel?
> > > > In theory it should be back-compatible for all Xen 3, but in
> > > > practice it tweaks lots of bugs in older Xens (particularly
> > > > 32-on-64).  I don't know that anyone has definitively established
> > > > an earliest version.  I implemented vcpu info placement for use in
> > > > pvops kernels, but it was never my intention that it be an
> > > > absolute requirement.
> > > >
> > > >      J
> > > Ok, attached  patch without BUG_ON. Please feel free to modify
> > > to your liking also.
> > It looks like you smashed all the tabs into spaces so its hard to see
> > what you've changed in the diff.  I'll fix it up and give it a
> > look-over.
> >
> >      J
> Sorry, I've tabs turned off because patches I submit to other product I
> work on must be tab free.  Anyways, re attached a new one with tabs.
This doesn't compile with CONFIG_SMP=n because setup_max_cpus doesn't 
exist.  For now I've just put a couple of #ifdef CONFIG_SMPs in there to 
avoid compile errors, but could you look at coming up with a cleaner 
solution?
Thanks,
    J


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