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Wed, 20 Apr 2022 09:01:12 -0700 (PDT) Received: from treble ([2600:1700:6e32:6c00::35]) by smtp.gmail.com with ESMTPSA id t4-20020ae9df04000000b0069e9a6734dbsm1709186qkf.11.2022.04.20.09.01.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Apr 2022 09:01:11 -0700 (PDT) Date: Wed, 20 Apr 2022 09:01:08 -0700 From: Josh Poimboeuf To: Peter Zijlstra Cc: x86@kernel.org, brgerst@gmail.com, jiangshanlai@gmail.com, Andrew.Cooper3@citrix.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] x86: Simplify Retpoline thunk Message-ID: <20220420160108.w3rxf3vhmgnnpplq@treble> References: <20220419204109.520779286@infradead.org> <20220419205241.280037046@infradead.org> <20220420152736.qzl3nikds6mq5nrr@treble> <20220420155116.GH2731@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220420155116.GH2731@worktop.programming.kicks-ass.net> X-Spam-Status: No, score=-3.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 20, 2022 at 05:51:16PM +0200, Peter Zijlstra wrote: > On Wed, Apr 20, 2022 at 08:27:36AM -0700, Josh Poimboeuf wrote: > > On Tue, Apr 19, 2022 at 10:41:10PM +0200, Peter Zijlstra wrote: > > > Now that we rewrite all the indirect call sites, per commit: > > > > > > 750850090081 ("x86/alternative: Implement .retpoline_sites support") > > > > > > it doesn't make sense to have the retpoline thunks be an ALTERNATIVE_2 > > > that still includes a 'naked' indirect jump. > > > > > > (this accidentally 'defunnels' i386 by going back to full retpolines) > > > > So mitigations=off no longer works on i386? > > Also true I suppose... does anybody care? /me runs like heck. > > I'd hate to make all this more complicated just because i386 tho :/ Not that I care... but at least the commit log should own up to it :-) -- Josh