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[209.85.128.41]) by smtp.gmail.com with ESMTPSA id op5-20020a170906bce500b009a1fef32ce6sm7423643ejb.177.2023.09.12.13.48.21 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Sep 2023 13:48:22 -0700 (PDT) Received: by mail-wm1-f41.google.com with SMTP id 5b1f17b1804b1-401d24f1f27so69211865e9.1 for ; Tue, 12 Sep 2023 13:48:21 -0700 (PDT) X-Received: by 2002:a05:600c:2288:b0:401:d803:6246 with SMTP id 8-20020a05600c228800b00401d8036246mr553079wmf.2.1694551701487; Tue, 12 Sep 2023 13:48:21 -0700 (PDT) MIME-Version: 1.0 References: <20230830140315.2666490-1-mjguzik@gmail.com> <27ba3536633c4e43b65f1dcd0a82c0de@AcuMS.aculab.com> <9a5dd401bf154a0aace0e5f781a3580c@AcuMS.aculab.com> In-Reply-To: From: Linus Torvalds Date: Tue, 12 Sep 2023 13:48:04 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2] x86: bring back rep movsq for user access on CPUs without ERMS To: David Laight Cc: Mateusz Guzik , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "bp@alien8.de" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Tue, 12 Sep 2023 13:48:30 -0700 (PDT) X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email On Tue, 12 Sept 2023 at 12:41, David Laight wrote: > > What I found seemed to imply that 'rep movsq' used the same internal > logic as 'rep movsb' (pretty easy to do in hardware) Christ. I told you. It's pretty easy in hardware AS LONG AS IT'S ALIGNED. And if it's unaligned, "rep movsq" is FUNDAMENTALLY HARDER. Really. Linus