linux-kernel - Re: [PATCH v6 04/10] x86/dt: Parse the Wakeup Mailbox for Intel processors

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Message-ID: <20251017221715.GE614927@liuwe-devbox-debian-v2.local>
Date: Fri, 17 Oct 2025 22:17:15 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc: x86@...nel.org, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Rob Herring <robh@...nel.org>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Michael Kelley <mhklinux@...look.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Saurabh Sengar <ssengar@...ux.microsoft.com>,
	Chris Oo <cho@...rosoft.com>, "Kirill A. Shutemov" <kas@...nel.org>,
	linux-hyperv@...r.kernel.org, devicetree@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ricardo Neri <ricardo.neri@...el.com>,
	Yunhong Jiang <yunhong.jiang@...ux.intel.com>
Subject: Re: [PATCH v6 04/10] x86/dt: Parse the Wakeup Mailbox for Intel
 processors

On Thu, Oct 16, 2025 at 07:57:26PM -0700, Ricardo Neri wrote:
> The Wakeup Mailbox is a mechanism to boot secondary CPUs 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. It will be set if a
> wakeup mailbox is enumerated via an ACPI table or a DeviceTree node. For
> cases in which this behavior is not desired, this APIC callback can be
> updated later during boot using platform-specific hooks.
> 
> Reviewed-by: Dexuan Cui <decui@...rosoft.com>
> 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>

Can I get an ack from x86 maintainers?

Wei