linux-kernel - Re: [PATCH v5 06/16] efi: Disable LASS around set_virtual_address

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Message-ID: <vp6kerur3lw7kkw4on5n4vflkdetwrj55dhndkmqn7eljrziyj@v6nhq4bz5ort>
Date: Tue, 29 Oct 2024 17:00:32 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ard Biesheuvel <ardb@...nel.org>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Xiongwei Song <xiongwei.song@...driver.com>, Xin Li <xin3.li@...el.com>, 
	"Mike Rapoport (IBM)" <rppt@...nel.org>, Brijesh Singh <brijesh.singh@....com>, 
	Michael Roth <michael.roth@....com>, Tony Luck <tony.luck@...el.com>, 
	Alexey Kardashevskiy <aik@....com>, Jonathan Corbet <corbet@....net>, 
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	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Daniel Sneddon <daniel.sneddon@...ux.intel.com>, 
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	Breno Leitao <leitao@...ian.org>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Alexei Starovoitov <ast@...nel.org>, Hou Tao <houtao1@...wei.com>, Juergen Gross <jgross@...e.com>, 
	Vegard Nossum <vegard.nossum@...cle.com>, Kees Cook <kees@...nel.org>, Eric Biggers <ebiggers@...gle.com>, 
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	Andrew Morton <akpm@...ux-foundation.org>, Luis Chamberlain <mcgrof@...nel.org>, 
	Yuntao Wang <ytcoode@...il.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, Tejun Heo <tj@...nel.org>, Changbin Du <changbin.du@...wei.com>, 
	Huang Shijie <shijie@...amperecomputing.com>, Geert Uytterhoeven <geert+renesas@...der.be>, 
	Namhyung Kim <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...hat.com>, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH v5 06/16] efi: Disable LASS around
 set_virtual_address_map call

On Mon, Oct 28, 2024 at 06:07:54PM +0200, Alexander Shishkin wrote:
> Of all the EFI runtime services, set_virtual_address_map is the only one

set_virtual_address_map()

> that is called at its lower mapping, which LASS prohibits regardless of
> EFLAGS.AC setting. The only way to allow this to happen is to disable
> LASS in the CR4 register.

How does it interact with cr_pinning? IIUC, this can happen well after
boot? Like on efivar fs mount.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov