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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, 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 45D60C433DF for ; Tue, 16 Jun 2020 10:33:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 187F020767 for ; Tue, 16 Jun 2020 10:33:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727966AbgFPKdR (ORCPT ); Tue, 16 Jun 2020 06:33:17 -0400 Received: from verein.lst.de ([213.95.11.211]:37487 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726052AbgFPKdR (ORCPT ); Tue, 16 Jun 2020 06:33:17 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 6DDF068AEF; Tue, 16 Jun 2020 12:33:13 +0200 (CEST) Date: Tue, 16 Jun 2020 12:33:13 +0200 From: Christoph Hellwig To: Peter Zijlstra Cc: Christoph Hellwig , Dexuan Cui , vkuznets , Stephen Hemminger , Andy Lutomirski , Andy Lutomirski , Michael Kelley , Ju-Hyoung Lee , "x86@kernel.org" , "linux-hyperv@vger.kernel.org" , "linux-kernel@vger.kernel.org" , KY Srinivasan , Tom Lendacky Subject: Re: hv_hypercall_pg page permissios Message-ID: <20200616103313.GA30833@lst.de> References: <87y2ooiv5k.fsf@vitty.brq.redhat.com> <20200616072318.GA17600@lst.de> <20200616101807.GO2531@hirez.programming.kicks-ass.net> <20200616102350.GA29684@lst.de> <20200616102412.GB29684@lst.de> <20200616103137.GQ2531@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200616103137.GQ2531@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Tue, Jun 16, 2020 at 12:31:37PM +0200, Peter Zijlstra wrote: > On Tue, Jun 16, 2020 at 12:24:12PM +0200, Christoph Hellwig wrote: > > On Tue, Jun 16, 2020 at 12:23:50PM +0200, Christoph Hellwig wrote: > > > > > + hv_hypercall_pg = module_alloc(PAGE_SIZE); > > > > if (hv_hypercall_pg == NULL) { > > > > wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0); > > > > goto remove_cpuhp_state; > > > > } > > > > > > > > + set_memory_ro((unsigned long)hv_hypercall_pg, 1); > > > > + set_memory_x((unsigned long)hv_hypercall_pg, 1); > > > > > > The changing of the permissions sucks. I thought about adding > > > a module_alloc_prot with an explicit pgprot_t argument. On x86 > > > alone at least ftrace would also benefit from that. > > How would ftrace benefit from a RX permission? We need to actually write > to the page first. This HV thing is special in that it lets the host > write. sorry, s/ftrace/kprobes/. See my updated branch here: http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/module_alloc-cleanup