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=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 1FBB6CA9EB9 for ; Wed, 23 Oct 2019 22:50:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E475820679 for ; Wed, 23 Oct 2019 22:50:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="dzTDdH1n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436888AbfJWWuB (ORCPT ); Wed, 23 Oct 2019 18:50:01 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:23159 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2436878AbfJWWuB (ORCPT ); Wed, 23 Oct 2019 18:50:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571871000; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Yz7wSvOGd82/0K8lGxn6yjb1/1nVsqdH855L2IiS7Z0=; b=dzTDdH1n0BKJ9o4PJ7hdXkJjMd5q5OBG6xKGHDzeMBRiZPQTR2mRCqMt5gDDWJjob1na1I oc0f14c5eFgIO3yf7kwb9dDK+Wv50S8q+HLIDaIkgsu1pWQJntgG7k96bFpuHzMbREr6JC fu3p3zMsFtXBHHEfqfqCxIFY8p+SonI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-208-ThLW4CDOM-6LSfmPyZOXsQ-1; Wed, 23 Oct 2019 18:49:58 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 11A351005500; Wed, 23 Oct 2019 22:49:57 +0000 (UTC) Received: from treble (ovpn-121-225.rdu2.redhat.com [10.10.121.225]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EECEE5C1D4; Wed, 23 Oct 2019 22:49:54 +0000 (UTC) Date: Wed, 23 Oct 2019 17:49:52 -0500 From: Josh Poimboeuf To: Thomas Gleixner Cc: LKML , x86@kernel.org, Peter Zijlstra , Andy Lutomirski , Will Deacon , Paolo Bonzini , kvm@vger.kernel.org, linux-arch@vger.kernel.org, Mike Rapoport , Miroslav Benes Subject: Re: [patch V2 03/17] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Message-ID: <20191023224952.d73mataiisu3u4tg@treble> References: <20191023122705.198339581@linutronix.de> <20191023123117.871608831@linutronix.de> <20191023213107.m7ishskghswktspp@treble> MIME-Version: 1.0 In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: ThLW4CDOM-6LSfmPyZOXsQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 24, 2019 at 12:35:27AM +0200, Thomas Gleixner wrote: > On Wed, 23 Oct 2019, Josh Poimboeuf wrote: >=20 > > On Wed, Oct 23, 2019 at 02:27:08PM +0200, Thomas Gleixner wrote: > > > That function returns immediately after conditionally reenabling inte= rrupts which > > > is more than pointless and requires the ASM code to disable interrupt= s again. > > >=20 > > > Signed-off-by: Thomas Gleixner > > > --- > > > arch/x86/kernel/traps.c | 1 - > > > 1 file changed, 1 deletion(-) > > >=20 > > > --- a/arch/x86/kernel/traps.c > > > +++ b/arch/x86/kernel/traps.c > > > @@ -871,7 +871,6 @@ do_simd_coprocessor_error(struct pt_regs > > > dotraplinkage void > > > do_spurious_interrupt_bug(struct pt_regs *regs, long error_code) > > > { > > > -=09cond_local_irq_enable(regs); > > > } > >=20 > > I think we can just remove this handler altogether. The Intel and AMD > > manuals say vector 15 (X86_TRAP_SPURIOUS) is reserved. >=20 > Right, but this has history. Pentium Pro Erratum: >=20 > PROBLEM: If the APIC subsystem is configured in mixed mode with Virtual > Wire mode implemented through the local APIC, an interrupt vector of 0F= h > (Intel reserved encoding) may be generated by the local APIC (Int 15). > This vector may be generated upon receipt of a spurious interrupt (an > interrupt which is removed before the system receives the INTA sequence= ) > instead of the programmed 8259 spurious interrupt vector. >=20 > IMPLICATION: The spurious interrupt vector programmed in the 8259 is > normally handled by an operating system=E2=80=99s spurious interrupt > handler. However, a vector of 0Fh is unknown to some operating systems, > which would crash if this erratum occurred. >=20 > Initially (2.1.) there was a printk() in that handler, which later got > ifdeffed out (2.1.54). >=20 > So I rather keep that thing at least as long as we support PPro :) Even i= f > we ditch that the handler is not really hurting anyone. Ah. I guess we could remove the idtentry for 64-bit then? Anyway the above would be a good comment for the function. --=20 Josh