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

[Julien Grall <julien.grall@xxxxxxx>]

(+ 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?
> The gic-v3 controller is configured with EOImode to 1, so during xen
> reboot, there is a function call "smp_call_function(halt_this_cpu, NULL, 0);"
> ,but halt_this_cpu never return, that means other CPUs have no chance to
s/,/, /

> deactive the SGI interrupt, because the deactivate_irq operation is at
s/deactive/deactivate/  

> the end of do_sgi. During xen booting again, CPU0 will issue
s/xen/Xen/

Also:

"During the next boot of Xen,"

> GIC_SGI_CALL_FUNCTION to other CPUs. Because GIC_SGI_CALL_FUNCTION of
> other CPUs are active during the last reboot, interrupts could not be
s/of other/on the others/

> triggered unless we deactivate the interrupt first.
I think it would be clearer if you say: "As the Active state for SGI is left 
untouched during the reboot, the GIC_SGI_CALL_FUNCTION will still be active on 
the non-boot CPUs. This means the interrupt cannot be triggered again until it 
get deactivated."
> To fix this issue, let's move the deactivate_irq operation just after
> eoi_irq, then the SGI interrupt will be in deactive state when
s/deactive/deactivate/

> smp_call_function_interrupt.
I would add: "This is fine because the interrupts are masked while handling the 
SGI.".
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
I think the patch makes sense in itself. This is a saner behavior than turning 
off the CPU with active interrupts. I want to double-check a few things before 
committing it. But I will definitely commit it by the end of the week.
No need to resend the patch if there are no changes in the code. I can take care 
for the commit message.
Cheers,

--
Julien Grall

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