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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Andres Freund <andres@anarazel.de>, Sasha Levin <sashal@kernel.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Zhang Rui <rui.zhang@intel.com>,
        Peter Zijlstra <peterz@infradead.org>, rafael@kernel.org,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        x86@kernel.org, linux-acpi@vger.kernel.org
Subject: Re: [PATCH AUTOSEL 6.6 02/17] x86/acpi: Ignore invalid x2APIC entries
In-Reply-To: <20231206070423.wp7cxxnwfe3lidm3@awork3.anarazel.de>
Date:   Tue, 12 Dec 2023 17:17:18 +0100
Message-ID: <8734w7qttd.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Tue, Dec 05 2023 at 23:04, Andres Freund wrote:
> On 2023-11-22 10:31:31 -0500, Sasha Levin wrote:
>> Currently, the kernel enumerates the possible CPUs by parsing both ACPI
>> MADT Local APIC entries and x2APIC entries. So CPUs with "valid" APIC IDs,
>> even if they have duplicated APIC IDs in Local APIC and x2APIC, are always
>> enumerated.
>
> As just described in
> https://lore.kernel.org/all/20231206065850.hs7k554v6wym7gw5@awork3.anarazel.de/
> and also previously described by John Sperbeck
> https://lore.kernel.org/all/20231122221947.781812-1-jsperbeck@google.com/
>
> this patch causes some machines to "loose" cpus. All but one in my
> case.

Sorry for the delay.

> Even if the commit didn't have these unintended consequences, it seems like a
> commit like this hardly is -stable material?

Shit happens. We are all human, right?