linux-kernel - Re: 4067196a5227 ("mm/page_alloc: fix deadlock on cpu_hotplug_lock in __accept_page()") (was: Re: [tip: x86/boot] x86/boot: Provide __pti_set_user

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Message-ID: <6xlb5o4fqzn6o3jojwvav7aln5uyiraox573zntxspjkwfbkzi@yx53iy4h7gw2>
Date: Tue, 6 May 2025 13:23:01 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Borislav Petkov <bp@...en8.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org, 
	Ingo Molnar <mingo@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	David Woodhouse <dwmw@...zon.co.uk>, Dionna Amalie Glaze <dionnaglaze@...gle.com>, 
	"H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>, 
	Kevin Loughlin <kevinloughlin@...gle.com>, Len Brown <len.brown@...el.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, 
	Tom Lendacky <thomas.lendacky@....com>, linux-efi@...r.kernel.org, x86@...nel.org, 
	Ard Biesheuvel <ardb@...nel.org>
Subject: Re: 4067196a5227 ("mm/page_alloc: fix deadlock on cpu_hotplug_lock
 in __accept_page()") (was: Re: [tip: x86/boot] x86/boot: Provide
 __pti_set_user_pgtbl() to startup code)

On Tue, May 06, 2025 at 11:24:45AM +0200, Borislav Petkov wrote:
> Fun stuff.

Ughh.. Thanks for digging into this.

The code around static_branch_inc/dec() getting way to complex for the
benefit that is only visible on microbenchmark.

Let's just remove it all.

I will prepare patches later today.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov