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

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Message-ID: <8734dnouq6.ffs@tglx>
Date: Fri, 02 May 2025 18:14:41 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Roman Kisel <romank@...ux.microsoft.com>, 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, romank@...ux.microsoft.com, russ.anderson@....com,
 steve.wahl@....com, 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
Cc: 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 13:47, 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>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>