linux-kernel - Re: [PATCH v10 13/19] irqchip/gic-v3: Don't return errors from gic_acpi_match

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Date: Wed, 19 Jun 2024 09:11:37 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>, "Catalin
 Marinas" <catalin.marinas@....com>, <linux-acpi@...r.kernel.org>,
	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
	<linuxarm@...wei.com>
CC: Mark Rutland <mark.rutland@....com>, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>, <loongarch@...ts.linux.dev>,
	<x86@...nel.org>, Russell King <linux@...linux.org.uk>, "Rafael J . Wysocki"
	<rafael@...nel.org>, "Miguel Luis" <miguel.luis@...cle.com>, James Morse
	<james.morse@....com>, "Salil Mehta" <salil.mehta@...wei.com>, Jean-Philippe
 Brucker <jean-philippe@...aro.org>, Hanjun Guo <guohanjun@...wei.com>, Gavin
 Shan <gshan@...hat.com>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	<justin.he@....com>, <jianyong.wu@....com>
Subject: Re: [PATCH v10 13/19] irqchip/gic-v3: Don't return errors from
 gic_acpi_match_gicc()

On Wed, 29 May 2024 14:34:40 +0100
Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:

> From: James Morse <james.morse@....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@....com>
> Reviewed-by: Gavin Shan <gshan@...hat.com>
> Tested-by: Miguel Luis <miguel.luis@...cle.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Sorry. I managed not to pick up Marc's RB form v8 and this patch is unchanged.
https://lore.kernel.org/all/87jzkktaui.wl-maz@kernel.org/

Hopefully whoever picks this up is using tooling (b4 or similar) that will get it from
here.

Reviewed-by: Marc Zyngier <maz@...nel.org>

So just patch 14 waiting for Marc to take another glance.


> ---
>  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)