linux-kernel - Re: [RFC][PATCH 0/8] x86/mm: Simplify PAE page table handling

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Message-ID: <Z5NIKGcgS2pMhZFn@8bytes.org>
Date: Fri, 24 Jan 2025 08:58:32 +0100
From: Joerg Roedel <joro@...tes.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
	bp@...en8.de, luto@...nel.org, kirill.shutemov@...ux.intel.com,
	rick.p.edgecombe@...el.com, jgross@...e.com
Subject: Re: [RFC][PATCH 0/8] x86/mm: Simplify PAE page table handling

On Thu, Jan 23, 2025 at 03:06:26PM -0800, Dave Hansen wrote:
> 32-bit+PTI or 32-bit in general? ;)

+1 for removing x86-32 bit support alltogether.

> I'm curious what Joerg and the other folks that worked on 32-bit PTI
> think about it in retrospect. The 32 vs. 64-bit security gap was
> probably modest in 2018 and it can only have grown since then.

I think the decision to keep and maintain 32-bit support only makes
sense if it can be kept on-par with x86-64 security-wise, otherwise we
are lying to our users about the 'supported' part. Back in the day when
I did the 32-bit PTI support it made sense, but that was 7 years ago.

When was the last 32-bit only x86 CPU sold?

> I definitely haven't seen a lot of 32-bit PTI bug reports.

That's because the 32-bit PTI support is a well crafted piece of beauty,
which was merged with almost no bugs ;-)


Regards,

	Joerg