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Re: [Xen-devel] [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?

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


the end of do_sgi. During xen booting again, CPU0 will issue



"During the next boot of Xen,"

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



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.


Julien Grall

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