linux-kernel - Re: [PATCH v5 05/16] x86/cpu: Defer CR pinning setup until after EFI initialization

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Message-ID: <gb5cwrzxvlkrca2luqmeysgo6vilbqo6iirx5r3lds7ge4vk3i@qdfr2y3o66yd>
Date: Wed, 30 Oct 2024 13:43:00 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: "H. Peter Anvin" <hpa@...or.com>, 
	"Hansen, Dave" <dave.hansen@...el.com>, "Mehta, Sohil" <sohil.mehta@...el.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, 
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	Xiongwei Song <xiongwei.song@...driver.com>, "Li, Xin3" <xin3.li@...el.com>, 
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	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v5 05/16] x86/cpu: Defer CR pinning setup until after EFI
 initialization

On Tue, Oct 29, 2024 at 11:18:29PM +0000, Luck, Tony wrote:
> >> Yeah, I was talking about 64-bit only.  On 32-bit PAE a PGD maps 1/4 of
> >> the address space which is totally unworkable for stealing.
> >
> > But it is also not necessary.
> 
> So maybe we could make the 64-bit version of use_temporary_mm()
> use some reserved address mapping to a reserved PGD in the upper
> half of address space, and the 32-bit version continue to use "user"
> addresses. It's unclear to me whether adding complexity here would be
> worth it to remove the 64-bit STAC/CLAC text patching issues.

Redesigning use_temporary_mm() is an interesting experiment, but it is
out of scope for the series.

LASS blocks LAM enabling. It would be nice to get LAM re-enabled soonish.

Maybe we can look at use_temporary_mm() again after LASS gets upstream?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov