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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 EAA38C32789 for ; Tue, 6 Nov 2018 13:11:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B05612085B for ; Tue, 6 Nov 2018 13:11:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kCrFfTT4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B05612085B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730513AbeKFWgh (ORCPT ); Tue, 6 Nov 2018 17:36:37 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:59010 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730421AbeKFWgh (ORCPT ); Tue, 6 Nov 2018 17:36:37 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=f4hpFykd27WZgb0tMujriu5Rm8XBUlMJV+J4NIrpLl8=; b=kCrFfTT4ZXzXUCEZk5Nv/PaeK txBrp5ZQiRyq7C5Jfi+jFZH8uNJ/pZvLIqiShhtGyABjdFTWJoNKy2Lk8YytKrb6ZjuvbPjpHBG0T EdouzxfDlbTKw9cvV3LALdWxxR2uaO1BB1csz3L8/LA3cCo+kL2svNkwXeUQICxZLhFkHDNxp7lRB tW86yC8G6nRPQKl92Ir6DsVHQOjFBH4ijakMTjCZm67IIzH06Jk9tcSfOs1W08S/j6j4yQRO7MD9/ gCanqQrw1tLi/PTublDLj0s0CSr9BlIIrgSUOXn0KrHwsmKsbRgGG9RU0b68DBr2018GIHoQUy8or qDIboiy/g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gK18a-0005G2-Tm; Tue, 06 Nov 2018 13:11:21 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6A15A20284F96; Tue, 6 Nov 2018 14:11:19 +0100 (CET) Date: Tue, 6 Nov 2018 14:11:19 +0100 From: Peter Zijlstra To: Nadav Amit Cc: Ingo Molnar , LKML , X86 ML , "H. Peter Anvin" , Thomas Gleixner , Borislav Petkov , Dave Hansen , Andy Lutomirski , Kees Cook , Dave Hansen , Masami Hiramatsu Subject: Re: [PATCH v3 6/7] x86/alternatives: use temporary mm for text poking Message-ID: <20181106131119.GA9828@hirez.programming.kicks-ass.net> References: <20181102232946.98461-1-namit@vmware.com> <20181102232946.98461-7-namit@vmware.com> <20181105133041.GC22467@hirez.programming.kicks-ass.net> <20181106082019.GF22431@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181106082019.GF22431@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 06, 2018 at 09:20:19AM +0100, Peter Zijlstra wrote: > By our current way of thinking, kmap_atomic simply is not correct. Something like the below; which weirdly builds an x86_32 kernel. Although I imagine a very sad one. --- diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index ba7e3464ee92..e273f3879d04 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1449,6 +1449,16 @@ config PAGE_OFFSET config HIGHMEM def_bool y depends on X86_32 && (HIGHMEM64G || HIGHMEM4G) + depends on !SMP || BROKEN + help + By current thinking kmap_atomic() is broken, since it relies on per + CPU PTEs in the global (kernel) address space and relies on CPU local + TLB invalidates to completely invalidate these PTEs. However there is + nothing that guarantees other CPUs will not speculatively touch upon + 'our' fixmap PTEs and load then into their TLBs, after which our + local TLB invalidate will not invalidate them. + + There are AMD chips that will #MC on inconsistent TLB states. config X86_PAE bool "PAE (Physical Address Extension) Support"