linux-kernel - Re: [PATCH RFC v3 10/21] ACPI: Check _STA present bit before making CPUs not present

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Message-ID: <20231215161803.00002d8c@Huawei.com>
Date: Fri, 15 Dec 2023 16:18:03 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
CC: <linux-pm@...r.kernel.org>, <loongarch@...ts.linux.dev>,
	<linux-acpi@...r.kernel.org>, <linux-arch@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-riscv@...ts.infradead.org>, <kvmarm@...ts.linux.dev>,
	<x86@...nel.org>, <acpica-devel@...ts.linuxfoundation.org>,
	<linux-csky@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<linux-ia64@...r.kernel.org>, <linux-parisc@...r.kernel.org>, Salil Mehta
	<salil.mehta@...wei.com>, Jean-Philippe Brucker <jean-philippe@...aro.org>,
	<jianyong.wu@....com>, <justin.he@....com>, James Morse <james.morse@....com>
Subject: Re: [PATCH RFC v3 10/21] ACPI: Check _STA present bit before making
 CPUs not present

On Wed, 13 Dec 2023 12:50:02 +0000
Russell King (Oracle) <rmk+kernel@...linux.org.uk> wrote:

> From: James Morse <james.morse@....com>
> 
> When called acpi_processor_post_eject() unconditionally make a CPU
> not-present and unregisters it.
> 
> To add support for AML events where the CPU has become disabled, but
> remains present, the _STA method should be checked before calling
> acpi_processor_remove().
> 
> Rename acpi_processor_post_eject() acpi_processor_remove_possible(), and
> check the _STA before calling.
> 
> Adding the function prototype for arch_unregister_cpu() allows the
> preprocessor guards to be removed.
> 
> After this change CPUs will remain registered and visible to
> user-space as offline if buggy firmware triggers an eject-request,
> but doesn't clear the corresponding _STA bits after _EJ0 has been
> called.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Miguel Luis <miguel.luis@...cle.com>
> Tested-by: Vishnu Pajjuri <vishnu@...amperecomputing.com>
> Tested-by: Jianyong Wu <jianyong.wu@....com>
LGTM
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>