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Date: Mon, 22 Apr 2024 11:39:10 +0100
From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: Thomas Gleixner <tglx@linutronix.de>, Peter Zijlstra
	<peterz@infradead.org>, <linux-pm@vger.kernel.org>,
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	<james.morse@arm.com>, Salil Mehta <salil.mehta@huawei.com>, Jean-Philippe
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CC: Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "Dave
 Hansen" <dave.hansen@linux.intel.com>, <justin.he@arm.com>,
	<jianyong.wu@arm.com>, Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH v7 10/16] irqchip/gic-v3: Don't return errors from
 gic_acpi_match_gicc()
Message-ID: <20240422113839.00000cde@huawei.com>
In-Reply-To: <20240418135412.14730-11-Jonathan.Cameron@huawei.com>
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	<20240418135412.14730-11-Jonathan.Cameron@huawei.com>
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On Thu, 18 Apr 2024 14:54:06 +0100
Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> From: James Morse <james.morse@arm.com>
> 
> gic_acpi_match_gicc() is only called via gic_acpi_count_gicr_regions().
> It should only count the number of enabled redistributors, but it
> also tries to sanity check the GICC entry, currently returning an
> error if the Enabled bit is set, but the gicr_base_address is zero.
> 
> Adding support for the online-capable bit to the sanity check will
> complicate it, for no benefit. The existing check implicitly depends on
> gic_acpi_count_gicr_regions() previous failing to find any GICR regions
> (as it is valid to have gicr_base_address of zero if the redistributors
> are described via a GICR entry).
> 
> Instead of complicating the check, remove it. Failures that happen at
> this point cause the irqchip not to register, meaning no irqs can be
> requested. The kernel grinds to a panic() pretty quickly.
> 
> Without the check, MADT tables that exhibit this problem are still
> caught by gic_populate_rdist(), which helpfully also prints what went
> wrong:
> | CPU4: mpidr 100 has no re-distributor!
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

I've been focused on the ACPI aspects until now, but now realize that this
and the next patch should have included the GIC maintainer in the
to list. I'll fix that for future versions, but for now

+CC Marc.
> ---
> v7: No change
> ---
>  drivers/irqchip/irq-gic-v3.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 6fb276504bcc..10af15f93d4d 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -2415,19 +2415,10 @@ static int __init gic_acpi_match_gicc(union acpi_subtable_headers *header,
>  	 * If GICC is enabled and has valid gicr base address, then it means
>  	 * GICR base is presented via GICC
>  	 */
> -	if (acpi_gicc_is_usable(gicc) && gicc->gicr_base_address) {
> +	if (acpi_gicc_is_usable(gicc) && gicc->gicr_base_address)
>  		acpi_data.enabled_rdists++;
> -		return 0;
> -	}
>  
> -	/*
> -	 * It's perfectly valid firmware can pass disabled GICC entry, driver
> -	 * should not treat as errors, skip the entry instead of probe fail.
> -	 */
> -	if (!acpi_gicc_is_usable(gicc))
> -		return 0;
> -
> -	return -ENODEV;
> +	return 0;
>  }
>  
>  static int __init gic_acpi_count_gicr_regions(void)