linux-kernel - Re: [PATCH] irqchip/irq-gic-v3-its.c: Return its_invall

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Date:   Wed, 08 Dec 2021 08:25:45 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Shaokun Zhang <zhangshaokun@...ilicon.com>
Cc:     linux-kernel@...r.kernel.org, Wudi Wang <wangwudi@...ilicon.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] irqchip/irq-gic-v3-its.c: Return its_invall_cmd.col when
 building INVALL

On 2021-12-08 01:54, Shaokun Zhang wrote:
> From: Wudi Wang <wangwudi@...ilicon.com>
> 
> INVALL CMD specifies that the ITS must ensure any caching associated 
> with
> the interrupt collection defined by ICID is consistent with the LPI
> configuration tables held in memory for all Redistributors. SYNC is
> required to ensure that INVALL is executed.

The patch title doesn't quite spell out the issue. It should say 
something
like:

"Force synchronisation when issuing INVALL"

> 
> Currently, LPI configuration data may be inconsistent with that in the
> memory within a short period of time after the INVALL command is 
> executed.

I'm curious: have you seen any issue with this on actual HW? In my
experience, all implementations treat INVALL as a synchronous command,

Or was this solely done via inspection?

> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Marc Zyngier <maz@...nel.org>
> Signed-off-by: Wudi Wang <wangwudi@...ilicon.com>
> Signed-off-by: Shaokun Zhang <zhangshaokun@...ilicon.com>

This needs:

Fixes: cc2d3216f53 ("irqchip: GICv3: ITS command queue")

> ---
>  drivers/irqchip/irq-gic-v3-its.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3-its.c 
> b/drivers/irqchip/irq-gic-v3-its.c
> index eb0882d15366..0cb584d9815b 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -742,7 +742,7 @@ static struct its_collection
> *its_build_invall_cmd(struct its_node *its,
> 
>  	its_fixup_cmd(cmd);
> 
> -	return NULL;
> +	return desc->its_invall_cmd.col;
>  }
> 
>  static struct its_vpe *its_build_vinvall_cmd(struct its_node *its,

I'll fix the above locally, no need to resend.

Thanks,

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