Re: [Xen-devel] [PATCH 5/7] xen/arm: wake up secondary cpus

[Tim Deegan <tim@xxxxxxx>]

At 16:59 +0100 on 24 Oct (1351097986), Stefano Stabellini wrote:
> On Wed, 24 Oct 2012, Tim Deegan wrote:
> > At 16:03 +0100 on 24 Oct (1351094625), Stefano Stabellini wrote:
> > > Secondary cpus are held by the firmware until we send an IPI to them.
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > ---
> > >  xen/arch/arm/head.S        |    8 ++++++--
> > >  xen/arch/arm/mode_switch.S |   31 +++++++++++++++++++++++++++++++
> > >  2 files changed, 37 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/xen/arch/arm/head.S b/xen/arch/arm/head.S
> > > index c784f4d..39c4774 100644
> > > --- a/xen/arch/arm/head.S
> > > +++ b/xen/arch/arm/head.S
> > > @@ -79,12 +79,12 @@ start:
> > >   beq   boot_cpu               /* If we're CPU 0, boot now */
> > >  
> > >   /* Non-boot CPUs wait here to be woken up one at a time. */
> > > -1:       wfe
> > > - dsb
> > > +1:       dsb
> > >   ldr   r0, =smp_up_cpu        /* VA of gate */
> > >   add   r0, r0, r10            /* PA of gate */
> > >   ldr   r1, [r0]               /* Which CPU is being booted? */
> > >   teq   r1, r12                /* Is it us? */
> > > + wfene
> > 
> > Shouldn't that be wf_i_ne?
> 
> Nope. We need wfe here, in fact the corresponding code is
> xen/arch/arm/smpboot.c:make_cpus_ready that uses sev to wake the other
> cpus up. The code running wfi on secondary cpus is actually in the
> firmware.

Ah, I see - thanks.

Tim.

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