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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 367DFC7EE33 for ; Wed, 24 May 2023 21:39:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232861AbjEXVj4 (ORCPT ); Wed, 24 May 2023 17:39:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230124AbjEXVjy (ORCPT ); Wed, 24 May 2023 17:39:54 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25277119 for ; Wed, 24 May 2023 14:39:53 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-564f529a663so16597367b3.1 for ; Wed, 24 May 2023 14:39:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1684964392; x=1687556392; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=u+lTI9LGfJCIeH9eUZOS37jnh9XivOrfiNHxwExkkPU=; b=1OM2n6A6XJR4jj8vE2JD/qVka6KhOa37sATKkJGdtzfw5ejGSX46cgRyM3KxfTglOD 0RNiltYW0aqpSJK1ylM7pyVuNywmw3i8GLhqy6D8KbpUnlsiq///5XlVQOyARTMakL95 sruDKzgA0kJWIRgwdNf60tHMZ2lnfSldT/PHutYtTTub50wqJp62S52UJsWvKQ7jpGPj JBND0HA8P6pXYHkEPXwT4zPgdYSplBBE7ttHpAHPL1RPyn6nSmxfEos2auwOVntQ9sEN x6n9gU3Z0Y/wI8zE55ONSW8DBiSo/6ReRvhBCmqYQEuA2BiS/6yDjqxNIpbAGpQ1wAiT KtGA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684964392; x=1687556392; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=u+lTI9LGfJCIeH9eUZOS37jnh9XivOrfiNHxwExkkPU=; b=Jzx7bHS9wLUdDUeKJfiamEzLPe5oSY97Zo26QAxGfLtepOQuwrurVFtt9hcTszr2Sd bY8vfn1N4S292p2JC/1mTcQg5S0dIhHLG0yffg9Qau6jJJmNeB9dnPZptyFB3KxIH01Z XXZgZieA/icC8WTr6o3EmVSMjvsV7uTXgjvUmhyVvwAik112BWhM+FwhDB+4nsfSjWN8 ulgY59PJQiAFOQ7I3FIobAi0OBAnRHJEjhFeCqN88uA3rkgeel+qZwv2ScDdE9m08Kdd jbd0pEOsPE1Do6vX7o3ojA97xxpDBHQk9Bsx69bbpKUFCHfUJTeRcpLC7qq/jtLAVnOH +h6w== X-Gm-Message-State: AC+VfDxT4VQNR9gIZAie/EpkNjH6DS68dSIBsxyrTJ1ga2O2j+MK1PK2 r3f0dj4NY9V51MZqbZHbcPJpQlTSMKs= X-Google-Smtp-Source: ACHHUZ4gGkG32f/WDPDY+8DnC86QiU6Z2uyq9N2VVLscH3WfhLiakxSPFeyk8pWCaiTnq1AgYyU2vpbztC4= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:ae14:0:b0:561:8bfb:feb1 with SMTP id m20-20020a81ae14000000b005618bfbfeb1mr12005442ywh.10.1684964392193; Wed, 24 May 2023 14:39:52 -0700 (PDT) Date: Wed, 24 May 2023 14:39:50 -0700 In-Reply-To: <20230524203336.GC3447678@hirez.programming.kicks-ass.net> Mime-Version: 1.0 References: <20220706082016.2603916-1-chao.p.peng@linux.intel.com> <20220706082016.2603916-9-chao.p.peng@linux.intel.com> <20230524203336.GC3447678@hirez.programming.kicks-ass.net> Message-ID: Subject: Re: [PATCH v7 08/14] KVM: Rename mmu_notifier_* From: Sean Christopherson To: Peter Zijlstra Cc: Kautuk Consul , Chao Peng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, linux-kselftest@vger.kernel.org, Paolo Bonzini , Jonathan Corbet , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 24, 2023, Peter Zijlstra wrote: > On Wed, May 24, 2023 at 01:16:03PM -0700, Sean Christopherson wrote: > > Of course, the only accesses outside of mmu_lock are reads, so on x86 that > > "atomic" access is just a READ_ONCE() load, but that's not the case for all > > architectures. > > This is true on *all* archs. atomic_set() and atomic_read() are no more > and no less than WRITE_ONCE() / READ_ONCE(). Ah, I take it s390's handcoded assembly routines are just a paranoid equivalents and not truly special? "l" and "st" do sound quite generic... commit 7657e41a0bd16c9d8b3cefe8fd5d6ac3c25ae4bf Author: Heiko Carstens Date: Thu Feb 17 13:13:58 2011 +0100 [S390] atomic: use inline asm Use inline assemblies for atomic_read/set(). This way there shouldn't be any questions or subtle volatile semantics left. static inline int __atomic_read(const atomic_t *v) { int c; asm volatile( " l %0,%1\n" : "=d" (c) : "R" (v->counter)); return c; } static inline void __atomic_set(atomic_t *v, int i) { asm volatile( " st %1,%0\n" : "=R" (v->counter) : "d" (i)); }