From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6BD3C433B4 for ; Fri, 14 May 2021 17:32:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89C9A613C8 for ; Fri, 14 May 2021 17:32:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233552AbhENReJ (ORCPT ); Fri, 14 May 2021 13:34:09 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:38202 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232394AbhENReH (ORCPT ); Fri, 14 May 2021 13:34:07 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1621013574; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3RJZ0XX14xM21R7lZUKkaNX6VVRciDvkJ2L8b2qH9qQ=; b=NM7jyIp9oak0LJEU6gjUrH7Bzvy+CrfWo6sfuI1FGJTf27TJi6MWwZ8GTvCWdMqYs46b+M FWaqQYJI3W8VZwxK9JcmHNT4709BESFWaRwgOA7JdZMJ7KXmzDmDP3h6npegW4y1Nj2hZJ kRaSC0L0G3TzSIqaVOSz/MHiErs3DGPggnRoaMCJW+NjQXLw8ggiQaHNonk5gnM48dDTHI 2PC1e9KqDilKYbiUWxioKQNAqWnujXEoHGJnzhGgsK3YfB5zXzlINtm9NyLR5k5GO6MC59 oeaV0iNNFG516GtAXqkaZ2UoXZ1anY7xhqdhOEfOLn5V0zx5pHzvYb0k6XrTog== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1621013574; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3RJZ0XX14xM21R7lZUKkaNX6VVRciDvkJ2L8b2qH9qQ=; b=NSRaJBxwjaaI6RAdX71Q+v4ctm/IH03z0eVZxmn5WwOfWwHCt8TRdNoM9mxGX/JNHlyC6h uXOw5YSYqjl8P3Dg== To: Maximilian Luz , Sachi King , Ingo Molnar , Borislav Petkov , David Laight Cc: "H. Peter Anvin" , "x86\@kernel.org" , "linux-kernel\@vger.kernel.org" , "stable\@vger.kernel.org" Subject: Re: [PATCH] x86/i8259: Work around buggy legacy PIC In-Reply-To: <5c08541a-2615-f075-a189-0462f1005007@gmail.com> References: <20210512210459.1983026-1-luzmaximilian@gmail.com> <3034083.sOBWI1P7ec@yuki> <5c08541a-2615-f075-a189-0462f1005007@gmail.com> Date: Fri, 14 May 2021 19:32:54 +0200 Message-ID: <87im3l43w9.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 14 2021 at 13:58, Maximilian Luz wrote: > On 5/14/21 9:41 PM, Sachi King wrote: > I'd assume that _some_ sort of interrupt setup is done by the BIOS/UEFI. > The UEFI on those devices is fairly well-featured, with touch support > via SPI and all. Furthermore, keyboard (also supported in the device's > UEFI) is handled via a custom UART protocol. Unless they rely on polling > for all of that, I believe they'd have to set up some interrupts. Polling would be truly surprising. > Although, as you mention later on, that could also be handled via the > IOAPIC and the PIC is actually not supposed to be used. Maybe some > legacy component that never got tested and just broke with some new > hardware/firmware revision without anyone noticing? And since Linux > still seems to rely on that, we might be the first to notice. That's a valid assumption. As I said, we can make IOAPIC work even w/o PIC. I'll have a look how much PIC assumptions are still around. Thanks, tglx