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Peter Anvin" Cc: Maciej Wieczor-Retman , 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 Message-ID: <20260323215049.GGacG1uc-PQLp9DqWo@fat_crate.local> References: <7312c9f2feab8aea4612ed9a1841e8c22f5f69b1.1774008873.git.m.wieczorretman@pm.me> <20260323163145.GGacFq8WW0t2uqZm91@fat_crate.local> <207ba0a6-5ebc-465a-8d54-6e5a99622a72@zytor.com> <20260323191905.GDacGSKaG4rEU8O4NA@fat_crate.local> <20260323205841.GFacGpgZDBOCCG9Y5u@fat_crate.local> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette