linux-kernel - Re: [PATCHv11 18/19] x86/acpi: Add support for CPU offlining for ACPI MADT wakeup method

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Date: Thu, 13 Jun 2024 16:56:36 +0200
From: Borislav Petkov <bp@...en8.de>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Elena Reshetova <elena.reshetova@...el.com>,
	Jun Nakajima <jun.nakajima@...el.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	"Kalra, Ashish" <ashish.kalra@....com>,
	Sean Christopherson <seanjc@...gle.com>,
	"Huang, Kai" <kai.huang@...el.com>,
	Ard Biesheuvel <ardb@...nel.org>, Baoquan He <bhe@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>, kexec@...ts.infradead.org,
	linux-hyperv@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Tao Liu <ltao@...hat.com>
Subject: Re: [PATCHv11 18/19] x86/acpi: Add support for CPU offlining for
 ACPI MADT wakeup method

On Thu, Jun 13, 2024 at 04:41:00PM +0300, Kirill A. Shutemov wrote:
> It is easy enough to do. See the patch below.

Thanks, will have a look.

> But I am not sure if I can justify it properly. If someone doesn't really
> need 5-level paging, disabling it at compile-time would save ~34K of
> kernel code with the configuration.
> 
> Is it worth saving ~100 lines of code?

Well, it goes both ways: is it worth saving ~34K kernel text and for that make
the code a lot less conditional, more readable, contain less ugly ifdeffery,
...?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette