On Wed, 13 Sep 2023 16:38:03 +0000
James Morse <james.morse@xxxxxxx> wrote:
> ACPI has two ways of describing processors in the DSDT. Either as a device
> object with HID ACPI0007, or as a type 'C' package inside a Processor
> Container. The ACPI processor driver probes CPUs described as devices, but
> not those described as packages.
>
Specification reference needed...
Terminology wise, I'd just refer to Processor() objects as I think they
are named objects rather than data terms like a package (Which include
a PkgLength etc)
> 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 packages in a processor container.
processor terms in a processor container.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
Otherwise looks fine to me.
Jonathan
> ---
> drivers/acpi/acpi_processor.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index c0839bcf78c1..b4bde78121bb 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -625,9 +625,31 @@ static struct acpi_scan_handler processor_handler = {
> },
> };
>
> +static acpi_status acpi_processor_container_walk(acpi_handle handle,
> + u32 lvl,
> + void *context,
> + void **rv)
> +{
> + struct acpi_device *adev;
> + acpi_status status;
> +
> + adev = acpi_get_acpi_dev(handle);
> + if (!adev)
> + return AE_ERROR;
> +
> + status = acpi_processor_add(adev, &processor_device_ids[0]);
> + acpi_put_acpi_dev(adev);
> +
> + return status;
> +}
> +
> static int acpi_processor_container_attach(struct acpi_device *dev,
> const struct acpi_device_id *id)
> {
> + acpi_walk_namespace(ACPI_TYPE_PROCESSOR, dev->handle,
> + ACPI_UINT32_MAX, acpi_processor_container_walk,
> + NULL, NULL, NULL);
> +
> return 1;
> }
>
