Re: [Xen-devel] [PATCH v2] gic: drop interrupts enabling on interrupts processing

[Julien Grall <julien.grall@xxxxxxx>]

On 6/10/19 4:49 PM, Andrii Anisov wrote:
> Hello Julien,
Hi Andrii,

> On 31.05.19 20:11, Julien Grall wrote:
>
> > Here my take on the commit message:
> >
> > gic_interrupt() was implemented using a loop to limit the cost of the 
> > trap if there are multiple interrupts pending.
> > At the moment, interrupts are unmasked by gic_interrupt() before 
> > calling do_{IRQ, LPI}(). In the case of handling an interrupt routed 
> > to guests, its priority will be dropped, via desc->handler->end() 
> > called from do_irq(), with interrupt unmasked.
> > In other words:
> >      - Until the priority is dropped, only higher priority interrupt 
> > can be received. Today, only Xen interrupts have higher priority.
> >      - As soon as priority is dropped, any interrupt can be received.
> >
> > This means the purpose of the loop in gic_interrupt() is defeated as 
> > all interrupts may get trapped earlier. To reinstate the purpose of 
> > the loop (and prevent the trap), interrupts should be masked when 
> > dropping the priority.
> > For interrupts routed to Xen, priority will always be dropped with 
> > interrupts masked. So the issue is not present. However, it means that 
> > we are pointless try to mask the interrupts.
> > To avoid conflicting behavior between interrupt handling, 
> > gic_interrupt() is now keeping interrupts masked and defer the 
> > decision to do_{LPI, IRQ}.
> It is OK with me.
>
> Are you waiting from me more of
I was. But I also had time to think about the commit message and I would 
be happy to commit with just what it is currently written.
I have now applied to my staging branch with my acked-by. I will commit 
it tonight.
Thank you for the patch,

--
Julien Grall

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