linux-kernel - Re: [PATCH v5 02/23] irqchip/gic-v4.1: Skip absent CPUs while iterating over redistributors

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Date:   Mon, 16 Mar 2020 18:10:19 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Marc Zyngier <maz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Robert Richter <rrichter@...vell.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Zenghui Yu <yuzenghui@...wei.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH v5 02/23] irqchip/gic-v4.1: Skip absent CPUs while
 iterating over redistributors

Hi Marc

On 3/4/20 9:33 PM, Marc Zyngier wrote:
> In a system that is only sparsly populated with CPUs, we can end-up with
sparsely
> redistributors structures that are not initialized. Let's make sure we
redistributor structures
> don't try and access those when iterating over them (in this case when
> checking we have a L2 VPE table).
> 
> Fixes: 4e6437f12d6e ("irqchip/gic-v4.1: Ensure L2 vPE table is allocated at RD level")
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>
> ---
>  drivers/irqchip/irq-gic-v3-its.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 83b1186ffcad..da883a691028 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -2452,6 +2452,10 @@ static bool allocate_vpe_l2_table(int cpu, u32 id)
>  	if (!gic_rdists->has_rvpeid)
>  		return true;
>  
> +	/* Skip non-present CPUs */
> +	if (!base)
> +		return true;
> +
>  	val  = gicr_read_vpropbaser(base + SZ_128K + GICR_VPROPBASER);
>  
>  	esz  = FIELD_GET(GICR_VPROPBASER_4_1_ENTRY_SIZE, val) + 1;
> 
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Eric