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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 DD742C34047 for ; Wed, 19 Feb 2020 15:31:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7B3F2465D for ; Wed, 19 Feb 2020 15:31:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726794AbgBSPba (ORCPT ); Wed, 19 Feb 2020 10:31:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:41066 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726664AbgBSPba (ORCPT ); Wed, 19 Feb 2020 10:31:30 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1484A24654; Wed, 19 Feb 2020 15:31:28 +0000 (UTC) Date: Wed, 19 Feb 2020 10:31:26 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org, Will Deacon , Marc Zyngier , Michael Ellerman , Petr Mladek Subject: Re: [PATCH v3 01/22] hardirq/nmi: Allow nested nmi_enter() Message-ID: <20200219103126.33f67cf3@gandalf.local.home> In-Reply-To: <20200219150744.428764577@infradead.org> References: <20200219144724.800607165@infradead.org> <20200219150744.428764577@infradead.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Feb 2020 15:47:25 +0100 Peter Zijlstra wrote: > Since there are already a number of sites (ARM64, PowerPC) that > effectively nest nmi_enter(), lets make the primitive support this > before adding even more. > > void SMIException(struct pt_regs *regs) > --- a/include/linux/hardirq.h > +++ b/include/linux/hardirq.h > @@ -71,7 +71,7 @@ extern void irq_exit(void); > printk_nmi_enter(); \ > lockdep_off(); \ > ftrace_nmi_enter(); \ > - BUG_ON(in_nmi()); \ > + BUG_ON(in_nmi() == NMI_MASK); \ > preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \ > rcu_nmi_enter(); \ > trace_hardirq_enter(); \ > --- a/include/linux/preempt.h > +++ b/include/linux/preempt.h > @@ -26,13 +26,13 @@ > * PREEMPT_MASK: 0x000000ff > * SOFTIRQ_MASK: 0x0000ff00 > * HARDIRQ_MASK: 0x000f0000 > - * NMI_MASK: 0x00100000 > + * NMI_MASK: 0x00f00000 > * PREEMPT_NEED_RESCHED: 0x80000000 > */ > #define PREEMPT_BITS 8 > #define SOFTIRQ_BITS 8 > #define HARDIRQ_BITS 4 > -#define NMI_BITS 1 > +#define NMI_BITS 4 > Probably should document somewhere (in a comment above nmi_enter()?) that we allow nmi_enter() to nest up to 15 times. -- Steve