From: Thomas Gleixner <tglx@linutronix.de>
To: "Fernando F. Mancera" <ffmancera@riseup.net>,
Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH RESEND] x86/cpu/topology: remove limit of CPUs due to noapic on x86_64
Date: Sun, 01 Dec 2024 14:49:32 +0100 [thread overview]
Message-ID: <87wmgjv7gz.ffs@tglx> (raw)
In-Reply-To: <8e7f8783-5745-46fd-9a95-a5ed36065f77@riseup.net>
On Mon, Nov 25 2024 at 16:13, Fernando F. Mancera wrote:
> On 25/11/2024 09:37, Ingo Molnar wrote:
>> So what's the motivation? Arguably the x86-64 boot option behavior was
>> weird: a working local APIC is very much needed to have an SMP system.
>>
>
> Sorry if I am wrong here but I am not an expert on the matter. I
> believed that "noapic" disables I/O APIC which handles external
> interrupts while the local APICs are still enabled as they are managed
> by "nolapic". If that is the case, SMP should still be possible.
>
> If both I/O APIC and Local APICs are disabled then the kernel should
> fallback to a single CPU mode. That is the behavior that kernel has with
> my patch.
>
> The motivation is to fix multiple users with systems that requires
> "noapic" to work and after the rework their systems are using a single CPU.
Sorry, my bad. I messed up the "noapic" option handling.
next prev parent reply other threads:[~2024-12-01 13:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-24 17:45 [PATCH RESEND] x86/cpu/topology: remove limit of CPUs due to noapic on x86_64 Fernando Fernandez Mancera
2024-11-25 8:37 ` Ingo Molnar
2024-11-25 15:13 ` Fernando F. Mancera
2024-12-01 13:49 ` Thomas Gleixner [this message]
2024-12-01 13:56 ` Thomas Gleixner
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