linux-kernel - Re: [PATCH hyperv-next v3] arch/x86: Provide the CPU number in the wakeup AP callback

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Message-ID: <aBl62kTEAnR790KF@liuwe-devbox-ubuntu-v2.tail21d00.ts.net>
Date: Tue, 6 May 2025 02:58:34 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Roman Kisel <romank@...ux.microsoft.com>
Cc: ardb@...nel.org, bp@...en8.de, dave.hansen@...ux.intel.com,
	decui@...rosoft.com, dimitri.sivanich@....com,
	haiyangz@...rosoft.com, hpa@...or.com, imran.f.khan@...cle.com,
	jacob.jun.pan@...ux.intel.com, jgross@...e.com,
	justin.ernst@....com, kprateek.nayak@....com, kyle.meyer@....com,
	kys@...rosoft.com, lenb@...nel.org, mingo@...hat.com,
	nikunj@....com, papaluri@....com, perry.yuan@....com,
	peterz@...radead.org, rafael@...nel.org, russ.anderson@....com,
	steve.wahl@....com, tglx@...utronix.de, thomas.lendacky@....com,
	tim.c.chen@...ux.intel.com, tony.luck@...el.com, wei.liu@...nel.org,
	xin@...or.com, yuehaibing@...wei.com, linux-acpi@...r.kernel.org,
	linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, apais@...rosoft.com, benhill@...rosoft.com,
	bperkins@...rosoft.com, sunilmut@...rosoft.com
Subject: Re: [PATCH hyperv-next v3] arch/x86: Provide the CPU number in the
 wakeup AP callback

On Wed, Apr 30, 2025 at 01:47:20PM -0700, Roman Kisel wrote:
> When starting APs, confidential guests and paravisor guests
> need to know the CPU number, and the pattern of using the linear
> search has emerged in several places. With N processors that leads
> to the O(N^2) time complexity.
> 
> Provide the CPU number in the AP wake up callback so that one can
> get the CPU number in constant time.
> 
> Suggested-by: Michael Kelley <mhklinux@...look.com>
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

Queued to hyperv-next. Thanks.