linux-kernel - Re: [PATCH RFC v3 02/21] ACPI: processor: Add support for processors described as container packages

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Message-ID: <ZXtB/+2kDtaz1Zf4@shell.armlinux.org.uk>
Date:   Thu, 14 Dec 2023 17:57:19 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
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 02/21] ACPI: processor: Add support for processors
 described as container packages

On Thu, Dec 14, 2023 at 05:36:26PM +0000, Jonathan Cameron wrote:
> On Wed, 13 Dec 2023 12:49:21 +0000
> Russell King (Oracle) <rmk+kernel@...linux.org.uk> wrote:
> 
> > From: James Morse <james.morse@....com>
> > 
> > ACPI has two ways of describing processors in the DSDT. From ACPI v6.5,
> > 5.2.12:
> > 
> > "Starting with ACPI Specification 6.3, the use of the Processor() object
> > was deprecated. Only legacy systems should continue with this usage. On
> > the Itanium architecture only, a _UID is provided for the Processor()
> > that is a string object. This usage of _UID is also deprecated since it
> > can preclude an OSPM from being able to match a processor to a
> > non-enumerable device, such as those defined in the MADT. From ACPI
> > Specification 6.3 onward, all processor objects for all architectures
> > except Itanium must now use Device() objects with an _HID of ACPI0007,
> > and use only integer _UID values."
> > 
> > Also see https://uefi.org/specs/ACPI/6.5/08_Processor_Configuration_and_Control.html#declaring-processors
> > 
> > Duplicate descriptions are not allowed, the ACPI processor driver already
> > parses the UID from both devices and containers. acpi_processor_get_info()
> > returns an error if the UID exists twice in the DSDT.
> > 
> > The missing probe for CPUs described as packages creates a problem for
> > moving the cpu_register() calls into the acpi_processor driver, as CPUs
> > described like this don't get registered, leading to errors from other
> > subsystems when they try to add new sysfs entries to the CPU node.
> > (e.g. topology_sysfs_init()'s use of topology_add_dev() via cpuhp)
> > 
> > To fix this, parse the processor container and call acpi_processor_add()
> > for each processor that is discovered like this. The processor container
> > handler is added with acpi_scan_add_handler(), so no detach call will
> > arrive.
> > 
> > Qemu TCG describes CPUs using processor devices in a processor container.
> > For more information, see build_cpus_aml() in Qemu hw/acpi/cpu.c and
> > https://uefi.org/specs/ACPI/6.5/08_Processor_Configuration_and_Control.html#processor-container-device
> > 
> > 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>
> > ---
> > Outstanding comments:
> >  https://lore.kernel.org/r/20230914145353.000072e2@Huawei.com
> Looks like you resolved those (were all patch description things).
> 
> So I'm happy.
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Great, I wasn't sure if I had resolved them to your satisfaction, so I
kept the reference to your original review. I've now removed it and
added your r-b. Thanks.

-- 
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