linux-kernel - RE: [EXTERNAL] [PATCH v5 04/10] x86/dt: Parse the Wakeup Mailbox for Intel processors

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Message-ID:
 <DS3PR21MB5878E8CCE452CAF760EA1F23BF08A@DS3PR21MB5878.namprd21.prod.outlook.com>
Date: Fri, 12 Sep 2025 20:41:32 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, "x86@...nel.org"
	<x86@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Rob Herring <robh@...nel.org>, KY Srinivasan
	<kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu
	<wei.liu@...nel.org>, Michael Kelley <mhklinux@...look.com>, "Rafael J.
 Wysocki" <rafael@...nel.org>
CC: "ssengar@...ux.microsoft.com" <ssengar@...ux.microsoft.com>, Chris Oo
	<cho@...rosoft.com>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Ricardo Neri
	<ricardo.neri@...el.com>, Yunhong Jiang <yunhong.jiang@...ux.intel.com>
Subject: RE: [EXTERNAL] [PATCH v5 04/10] x86/dt: Parse the Wakeup Mailbox for
 Intel processors

> From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> Sent: Friday, June 27, 2025 8:35 PM
> [...]
> The Wakeup Mailbox is a mechanism to boot secondary CPUs used on systems
> that do not want or cannot use the INIT + StartUp IPI messages.
> 
> The platform firmware is expected to implement the mailbox as described in
> the Multiprocessor Wakeup Structure of the ACPI specification. It is also
> expected to publish the mailbox to the operating system as described in the
> corresponding DeviceTree schema that accompanies the documentation of the
> Linux kernel.
> 
> Reuse the existing functionality to set the memory location of the mailbox
> and update the wakeup_secondary_cpu_64() APIC callback. Make this
> functionality available to DeviceTree-based systems by making CONFIG_X86_
> MAILBOX_WAKEUP depend on either CONFIG_OF or
> CONFIG_ACPI_MADT_WAKEUP.
> 
> do_boot_cpu() uses wakeup_secondary_cpu_64() when set. If a wakeup
> mailbox
> is found (enumerated via an ACPI table or a DeviceTree node) it will be
> used unconditionally. For cases in which this behavior is not desired, this
> APIC callback can be updated later during boot using platform-specific
> hooks.
> 
> Co-developed-by: Yunhong Jiang <yunhong.jiang@...ux.intel.com>
> Signed-off-by: Yunhong Jiang <yunhong.jiang@...ux.intel.com>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> ---

LGTM

Reviewed-by: Dexuan Cui <decui@...rosoft.com>