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Re: [Xen-devel] [PATCH for-4.12 v2] arm: gic-v3: deactivate SGI/PPI during initialization


We spoke about SPIs in the previous version. Why aren't they de-activated here?

On 1/30/19 2:00 PM, 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.

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
deactivate the SGI interrupt, because the deactivate_irq operation is at
the end of do_sgi. During the next boot of Xen, CPU0 will issue
GIC_SGI_CALL_FUNCTION to other CPUs. 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.

And according to IHI0069D_gic_architecture_specification, chapter
"8.11.3 GICR_ICACTIVER0, Interrupt Clear-Active Register 0", the RW
field of GICR_ICACTIVER0 resets to a value that is architecturally UNKNOWN.

So set a fixed value during gic-v3 initialization to make sure
interrupts are in deactivated state.

It is a bit unclear what you mean by "fixed value" here. The only thing you do is clearing active state. So a better wording is "So make sure all interrupts are deactivated at during initialization by clearing the state".

How about SPIs?


Julien Grall

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