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Date:   Wed, 29 Sep 2021 16:32:42 +0800
From:   Pingfan Liu <piliu@redhat.com>
To:     Marc Zyngier <maz@kernel.org>
Cc:     Pingfan Liu <kernelfans@gmail.com>,
        linux-arm-kernel@lists.infradead.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Joey Gouly <joey.gouly@arm.com>,
        Sami Tolvanen <samitolvanen@google.com>,
        Julien Thierry <julien.thierry@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Yuichi Ito <ito-yuichi@fujitsu.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 5/5] irqchip/GICv3: make reschedule-ipi light weight
Message-ID: <YVQkqnlOdZJ7QhJv@piliu.users.ipa.redhat.com>
References: <20210924132837.45994-1-kernelfans@gmail.com>
 <20210924132837.45994-6-kernelfans@gmail.com>
 <87lf3fu9n1.wl-maz@kernel.org>
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On Wed, Sep 29, 2021 at 08:24:34AM +0100, Marc Zyngier wrote:
> On Fri, 24 Sep 2021 14:28:37 +0100,
> Pingfan Liu <kernelfans@gmail.com> wrote:
> > 
> > To achieve the light weight as
> > DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_reschedule_ipi) on x86, it had
> > better treat irqnr differently at the frontend. And let IPI_RESCHEDULE
> > call __irq_enter_raw() instead of irq_enter_rcu().
> > 
> > Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: Marc Zyngier <maz@kernel.org>
> > Cc: Joey Gouly <joey.gouly@arm.com>
> > Cc: Sami Tolvanen <samitolvanen@google.com>
> > Cc: Julien Thierry <julien.thierry@arm.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Yuichi Ito <ito-yuichi@fujitsu.com>
> > Cc: linux-kernel@vger.kernel.org
> > To: linux-arm-kernel@lists.infradead.org
> > ---
> >  drivers/irqchip/irq-gic-v3.c | 15 +++++++++++++--
> >  1 file changed, 13 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> > index 906538fa8771..593d4539a209 100644
> > --- a/drivers/irqchip/irq-gic-v3.c
> > +++ b/drivers/irqchip/irq-gic-v3.c
> > @@ -709,6 +709,9 @@ static void gic_handle_nmi(struct pt_regs *regs)
> >  		gic_deactivate_unhandled(irqnr);
> >  }
> >  
> > +/* RESCHEDULE IPI hwirq nr is 0, and the only raw one */
> > +static unsigned long raw_interrupt_mask = 1;
> 
> I'm afraid you have the wrong end of the stick. This isn't a GIC
> property. This is an architecture decision, and only the architecture
> can expose what they want.
> 
Could it done be export an interface int (*get_irq_nr)(pte_regs) to
do_interrupt_handler()? So it can be seen as an architecture
decision.


Thanks,

	Pingfan
> 
> -- 
> Without deviation from the norm, progress is not possible.
> 
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