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: <87zfq150r6.wl-maz@kernel.org>
Date: Sun, 28 Jul 2024 10:22:53 +0100
From: Marc Zyngier <maz@...nel.org>
To: Sasha Levin <sashal@...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, 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.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.