linux-kernel - Re: [PATCH 2/3] irqchip/gic-v3-its: Spin off GICv4 init into a separate function

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Message-ID: <ZdnM0DDsGCTPMpwl@linux.dev>
Date: Sat, 24 Feb 2024 11:02:40 +0000
From: Oliver Upton <oliver.upton@...ux.dev>
To: Marc Zyngier <maz@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Zenghui Yu <yuzenghui@...wei.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev, Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH 2/3] irqchip/gic-v3-its: Spin off GICv4 init into a
 separate function

On Sat, Feb 24, 2024 at 10:30:04AM +0000, Marc Zyngier wrote:
> On Mon, 19 Feb 2024 18:58:07 +0000, Oliver Upton <oliver.upton@...ux.dev> wrote:
> > @@ -3193,7 +3210,8 @@ static void its_cpu_init_lpis(void)
> >  		 * ancient programming gets left in and has possibility of
> >  		 * corrupting memory.
> >  		 */
> > -		val = its_clear_vpend_valid(vlpi_base, 0, 0);
> > +		its_clear_vpend_valid(vlpi_base, 0, 0);
> > +		return;
> 
> I'm not sure about the necessity of this return statement.
> allocate_vpe_l1_table() checks for rvpeid already, so it should be
> fine to carry on.

Yup, definitely not necessary. My aim was to have the control flow make
it a bit more obvious to the reader what's going on.

Having what reads as an allocation helper do a feature check isn't
entirely obvious.

I have no opinion either way though.

> >  	}
> >  
> >  	if (allocate_vpe_l1_table()) {
> > @@ -3205,15 +3223,6 @@ static void its_cpu_init_lpis(void)
> >  		gic_rdists->has_rvpeid = false;
> >  		gic_rdists->has_vlpis = false;
> >  	}
> > -
> > -	/* Make sure the GIC has seen the above */
> > -	dsb(sy);
> 
> ... we're now missing a dsb affecting the VPE table programming, as we
> expect things to take effect immediately.

LOL, and on the back of a bugfix no less. I'll fix this.

-- 
Thanks,
Oliver