linux-kernel - Re: [PATCH] arm64/irq: report bug if NR_IPI greater than max SGI during compile time

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Message-ID: <0f230af42ff4c6e4cf763b9145fb9487@kernel.org>
Date:   Tue, 08 Dec 2020 09:31:09 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/irq: report bug if NR_IPI greater than max SGI
 during compile time

On 2020-12-08 09:21, Pingfan Liu wrote:
> Although there is a runtime WARN_ON() when NR_IPR > max SGI, it had 
> better
> do the check during built time, and associate these related code 
> together.
> 
> Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Jason Cooper <jason@...edaemon.net>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> To: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  arch/arm64/kernel/smp.c                | 2 ++
>  drivers/irqchip/irq-gic-v3.c           | 2 +-
>  drivers/irqchip/irq-gic.c              | 2 +-
>  include/linux/irqchip/arm-gic-common.h | 2 ++
>  4 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 18e9727..9fc383c 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -33,6 +33,7 @@
>  #include <linux/kernel_stat.h>
>  #include <linux/kexec.h>
>  #include <linux/kvm_host.h>
> +#include <linux/irqchip/arm-gic-common.h>
> 
>  #include <asm/alternative.h>
>  #include <asm/atomic.h>
> @@ -76,6 +77,7 @@ enum ipi_msg_type {
>  	IPI_WAKEUP,
>  	NR_IPI
>  };
> +static_assert(NR_IPI <= MAX_SGI_NUM);

I am trying *very hard* to remove dependencies between the architecture
code and random drivers, so this kind of check really is 
counter-productive.

Driver code should not have to know the number of IPIs, because there is
no requirement that all IPIs should map 1:1 to SGIs. Conflating the two
is already wrong, and I really don't want to add more of that.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...