Re: [Xen-devel] [PATCH v7 01/10] x86/hypervisor: make hypervisor_ap_setup return an error code

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Feb 04, 2020 at 04:48:05PM +0000, Wei Liu wrote:
> On Tue, Feb 04, 2020 at 03:36:55PM +0000, Wei Liu wrote:
> > We want to be able to handle AP setup error in the upper layer.
> > 
> > For Xen, remove all panic() and BUG_ON() in init_evtchn and
> > map_vcpuinfo. Only panic/BUG_ON when Xen can't fail gracefully.
> > 
> > Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
> > ---
> 
> BTW I discover an issue: init_evtchn sets HVM_PARAM_CALLBACK_IRQ every
> time it is called. That's unnecessary for APs. Perhaps it would be best
> to break that function into two, one for setting HVM_PARAM_CALLBACK_IRQ,
> the other for allocating and setting callback. BSP needs to call both
> while APs only needs to call the latter.

We could gate the call to HVMOP_set_param on !smp_processor_id(), that
way the BSP would be the only one to set HVM_PARAM_CALLBACK_IRQ. I'm
not sure splitting this into a separate function is worth it.

Thanks, Roger.

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