linux-kernel - Re: [EXTERNAL] [PATCH v5 10/10] x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs

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Message-ID: <20250919024739.GB9139@ranerica-svr.sc.intel.com>
Date: Thu, 18 Sep 2025 19:47:39 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: Dexuan Cui <decui@...rosoft.com>
Cc: "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>,
	"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>
Subject: Re: [EXTERNAL] [PATCH v5 10/10] x86/hyperv/vtl: Use the wakeup
 mailbox to boot secondary CPUs

On Fri, Sep 12, 2025 at 08:47:52PM +0000, Dexuan Cui wrote:
> > From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> > Sent: Friday, June 27, 2025 8:35 PM
> > [...]
> > The hypervisor is an untrusted entity for TDX guests. It cannot be used
> > to boot secondary CPUs. The function hv_vtl_wakeup_secondary_cpu() cannot
> > be used.
> > 
> > Instead, the virtual firmware boots the secondary CPUs and places them in
> > a state to transfer control to the kernel using the wakeup mailbox.
> > 
> > The kernel updates the APIC callback wakeup_secondary_cpu_64() to use
> > the mailbox if detected early during boot (enumerated via either an ACPI
> > table or a DeviceTree node).
> > 
> > Reviewed-by: Michael Kelley <mhklinux@...look.com>
> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> > ---
> 
> LGTM
> 
> Reviewed-by: Dexuan Cui <decui@...rosoft.com>

Thank you for your review!