From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id C394B6B026F for ; Wed, 1 Nov 2017 18:30:05 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id e8so2000478wmc.2 for ; Wed, 01 Nov 2017 15:30:05 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id q197si1592455wmb.236.2017.11.01.15.30.04 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Wed, 01 Nov 2017 15:30:04 -0700 (PDT) Date: Wed, 1 Nov 2017 23:30:01 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCH 04/23] x86, tlb: make CR4-based TLB flushes more robust In-Reply-To: Message-ID: References: <20171031223146.6B47C861@viggo.jf.intel.com> <20171031223154.67F15B2A@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, luto@kernel.org, torvalds@linux-foundation.org, keescook@google.com, hughd@google.com, x86@kernel.org On Wed, 1 Nov 2017, Dave Hansen wrote: > On 11/01/2017 02:25 PM, Thomas Gleixner wrote: > >> cr4 = this_cpu_read(cpu_tlbstate.cr4); > >> - /* clear PGE */ > >> - native_write_cr4(cr4 & ~X86_CR4_PGE); > >> - /* write old PGE again and flush TLBs */ > >> + /* > >> + * This function is only called on systems that support X86_CR4_PGE > >> + * and where always set X86_CR4_PGE. Warn if we are called without > >> + * PGE set. > >> + */ > >> + WARN_ON_ONCE(!(cr4 & X86_CR4_PGE)); > > Because if CR4_PGE is not set, this warning triggers. So this defeats the > > toggle mode you are implementing. > > The warning is there because there is probably plenty of *other* stuff > that breaks if we have X86_FEATURE_PGE=1, but CR4.PGE=0. > > The point of this was to make this function do the right thing no matter > what, but warn if it gets called in an unexpected way. Fair enough. Can you please reflect that in the changelog ? Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org