linux-kernel - Re: [PATCH AUTOSEL 6.10 14/16] irqchip/gic-v3: Don't return errors from gic_acpi_match

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Message-ID: <Zrcuvkiol0PsKu0l@sashalap>
Date: Sat, 10 Aug 2024 05:11:26 -0400
From: Sasha Levin <sashal@...nel.org>
To: Marc Zyngier <maz@...nel.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	James Morse <james.morse@....com>, Gavin Shan <gshan@...hat.com>,
	Miguel Luis <miguel.luis@...cle.com>,
	Russell King <rmk+kernel@...linux.org.uk>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>, tglx@...utronix.de,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH AUTOSEL 6.10 14/16] irqchip/gic-v3: Don't return errors
 from gic_acpi_match_gicc()

On Sun, Jul 28, 2024 at 10:22:53AM +0100, Marc Zyngier wrote:
>On Sun, 28 Jul 2024 01:47:31 +0100,
>Sasha Levin <sashal@...nel.org> wrote:
>>
>> From: James Morse <james.morse@....com>
>>
>> [ Upstream commit fa2dabe57220e6af78ed7a2f7016bf250a618204 ]
>>
>> 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>
>> Reviewed-by: Marc Zyngier <maz@...nel.org>
>> Link: https://lore.kernel.org/r/20240529133446.28446-14-Jonathan.Cameron@huawei.com
>> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>Please drop this. It has no purpose being backported to stable.

Ack, thanks!

-- 
Thanks,
Sasha