From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Maciej Wieczor-Retman <m.wieczorretman@pm.me>,
tglx@kernel.org, peterz@infradead.org, xin@zytor.com,
maciej.wieczor-retman@intel.com, babu.moger@amd.com,
chang.seok.bae@intel.com, sohil.mehta@intel.com,
dave.hansen@linux.intel.com, jpoimboe@kernel.org,
elena.reshetova@intel.com, pawan.kumar.gupta@linux.intel.com,
ak@linux.intel.com, darwi@linutronix.de, mingo@redhat.com,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v11 3/4] x86/cpu: Do a sanity check on required feature bits
Date: Mon, 23 Mar 2026 15:03:34 -0700 [thread overview]
Message-ID: <AF8D364A-F217-40B2-AFD5-007600A60879@zytor.com> (raw)
In-Reply-To: <20260323215049.GGacG1uc-PQLp9DqWo@fat_crate.local>
On March 23, 2026 2:50:49 PM PDT, Borislav Petkov <bp@alien8.de> wrote:
>On Mon, Mar 23, 2026 at 02:40:47PM -0700, H. Peter Anvin wrote:
>> I did: the PAE case, which was not hypothetical. I'm sure I can dig up more.
>
>So let's start our justification from this POV: we have use cases X and Y and they
>would profit from getting these warning checks about required features not
>being set.
>
>I still am not persuaded that we want Linux to boot on those. Because those
>CPUs are clearly "out of whack" and they would work by pure luck.
>
>But I don't know anything about the particular snafus that happened there.
>
>To take your example, the BIOS vendor disabled PAE. Do you really wanna deal
>with fixing that? I mean, what else is b0rked there...?
>
>So frankly, I'd turn that taint into a panic.
>
>Because this CPU sounds to me like an all-bets-are-off thing.
>
Yes, hence the tainting.
The PAE case is historic, but it was a concrete example I had in my head where this issue You also of course mention BIOS settings and there are VMs ...
next prev parent reply other threads:[~2026-03-23 22:04 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 12:50 [PATCH v11 0/4] x86: Capability bits fix and required bits sanity check Maciej Wieczor-Retman
2026-03-20 12:50 ` [PATCH v11 1/4] x86/cpu: Clear feature bits disabled at compile-time Maciej Wieczor-Retman
2026-03-20 12:50 ` [PATCH v11 2/4] x86/cpu: Check if feature string is non-zero Maciej Wieczor-Retman
2026-03-23 14:24 ` Borislav Petkov
2026-03-23 15:52 ` Maciej Wieczor-Retman
2026-03-23 16:23 ` Borislav Petkov
2026-03-23 16:58 ` Maciej Wieczor-Retman
2026-03-23 17:51 ` Borislav Petkov
2026-03-23 18:11 ` Maciej Wieczor-Retman
2026-03-23 18:15 ` H. Peter Anvin
2026-03-20 12:50 ` [PATCH v11 3/4] x86/cpu: Do a sanity check on required feature bits Maciej Wieczor-Retman
2026-03-21 0:31 ` Pawan Gupta
2026-03-21 5:58 ` Maciej Wieczór-Retman
2026-03-23 18:16 ` Pawan Gupta
2026-03-23 18:33 ` Maciej Wieczor-Retman
2026-03-26 18:36 ` Maciej Wieczor-Retman
2026-03-26 19:04 ` Pawan Gupta
2026-03-26 19:11 ` Maciej Wieczor-Retman
2026-03-28 1:52 ` H. Peter Anvin
2026-03-28 2:01 ` H. Peter Anvin
2026-03-30 9:47 ` Maciej Wieczor-Retman
2026-03-30 10:09 ` Maciej Wieczor-Retman
2026-03-30 16:01 ` Pawan Gupta
2026-03-30 21:24 ` David Laight
2026-03-31 8:12 ` Maciej Wieczor-Retman
2026-03-31 13:29 ` Maciej Wieczor-Retman
2026-03-23 16:31 ` Borislav Petkov
2026-03-23 17:05 ` Maciej Wieczor-Retman
2026-03-23 17:55 ` Borislav Petkov
2026-03-23 18:43 ` H. Peter Anvin
2026-03-23 18:43 ` H. Peter Anvin
2026-03-23 19:19 ` Borislav Petkov
2026-03-23 20:24 ` H. Peter Anvin
2026-03-23 20:58 ` Borislav Petkov
2026-03-23 21:40 ` H. Peter Anvin
2026-03-23 21:50 ` Borislav Petkov
2026-03-23 21:56 ` Borislav Petkov
2026-03-23 22:03 ` H. Peter Anvin [this message]
2026-03-23 22:09 ` Borislav Petkov
2026-03-24 1:16 ` H. Peter Anvin
2026-03-20 12:50 ` [PATCH v11 4/4] x86/cpu: Clear feature bits whose dependencies were cleared Maciej Wieczor-Retman
2026-03-23 16:35 ` Borislav Petkov
2026-03-23 17:23 ` Maciej Wieczor-Retman
2026-03-23 17:59 ` Borislav Petkov
2026-03-23 18:18 ` Maciej Wieczor-Retman
2026-03-23 18:57 ` H. Peter Anvin
2026-03-23 19:30 ` Borislav Petkov
2026-03-25 9:33 ` Maciej Wieczor-Retman
2026-03-23 19:33 ` Ahmed S. Darwish
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