Re: [Xen-devel] [PATCH for-4.12] arm: gic: deactivate sgi immediately after eoi

[Julien Grall <julien.grall@xxxxxxx>]

On 30/01/2019 01:21, Peng Fan wrote:
> Hi Julien
Hi Peng,

> > -----Original Message-----
> > From: Julien Grall [mailto:julien.grall@xxxxxxx]
> > Sent: 2019年1月29日 23:57
> > To: Peng Fan <peng.fan@xxxxxxx>; sstabellini@xxxxxxxxxx; jgross@xxxxxxxx
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Andre Przywara
> > <andre.przywara@xxxxxxx>
> > Subject: Re: [PATCH for-4.12] arm: gic: deactivate sgi immediately after eoi
> >
> > (+ Andre)
> >
> > Hi Peng,
> >
> > On 24/01/2019 12:43, Peng Fan wrote:
> > > On i.MX8, we implemented partition reboot which means Cortex-A reboot
> > > will not impact M4 cores and System control Unit core. However GICv3
> > > is not reset because we also need to support A72 Cluster reboot
> > > without affecting A53 Cluster.
> > How about the other interrupts? For instance, it would be theoretically
> > possible to have a PPI/SPI active and receive the order to turn it off. Is this
> > going to be an issue?
> Currently we only met this issue when doing Xen reboot, because halt_this_cpu 
> never return.
> For other interrupts, I think they are deactivated properly.
I don't think so, IPIs has an higher priority than all the other interrupt. So 
you may receive the IPI while handling another interrupts. This will leave the 
interrupts activated while turning off the processor.
I spoke with Marc Z. (GIC expert) today regarding rebooting/kexecing with 
interrupts activated. He said this is a valid case and the boot code should take 
care of de-activating all interrupts. So your first patch might be more suitable 
here. Sorry for the inconvenience. I will comment back on the first one again.
Cheers,

--
Julien Grall

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