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=-15.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 61757C07E99 for ; Mon, 12 Jul 2021 20:20:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 436EE61248 for ; Mon, 12 Jul 2021 20:20:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234335AbhGLUXq (ORCPT ); Mon, 12 Jul 2021 16:23:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230284AbhGLUXp (ORCPT ); Mon, 12 Jul 2021 16:23:45 -0400 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64A65C0613DD for ; Mon, 12 Jul 2021 13:20:56 -0700 (PDT) Received: by mail-pj1-x102c.google.com with SMTP id p4-20020a17090a9304b029016f3020d867so704312pjo.3 for ; Mon, 12 Jul 2021 13:20:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=8o2qA0jse1VOvFPFaD6PgYYLJfCn5VH7o/A/Icr1vKc=; b=KUMSx4IiytM86cklRmiMj8llxA+f2mJDuBPdHoLG55KZsSMpTqrb7Hvf5mskjMKU9q lmtBj9d9luDpxPeSiVnM7OJ2zc8qlWZRNu/y65Z7YWP0JS2RMtruTj2sYrZFAnpMv19v zTxKiceNTnB1WZGfHfgPtr/SQ9kT+qVEJ5ynC9d+mvyVy2UtB2ftBQodMz7/tnnDVrOj GKtYYScJWN/UIXqz8lkLFXqh17or7wCxG/9lO69tcV/Ah3I6jqVRHyRX2aACmTXvJsoG Y1DxBGvSd0pLNI1Hzbrt2+H7aWUM58W4/n3NgM0fiBbGAZ0qnIKB7ABO63xyGOMK2859 xjKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=8o2qA0jse1VOvFPFaD6PgYYLJfCn5VH7o/A/Icr1vKc=; b=l/vHBYSvOhYsCgk/zizU7DKWcVQovYy8ddWaznifNv0o30fqOvBFHgFNAFfKepwlEv gexM26CjbyZGh8BqzEKkvd8hQg4uSnU+cpXyEbmqdw6NwGdrqZ3WlW1Zt4MbtUZXh90X nE8/dHXWLXKpYhat+EiOo//iExpdLF2FnGlm18sePippGdzOXT3CZ0o72J1el4XYkGt8 J0E3jydZBEMlGq+J87LPelzetEH4C/fr98BgNdCfoNkF+SKOe0Yv85wugJY2tx9n7OXE I7oua64kAbS1Rr+fc25/FSRy5v9N7yX1bnd2oiMvxz5fyXAU9eveFuD355OIhJa074Kt WCEQ== X-Gm-Message-State: AOAM5322qef4b5GYSyW8kGSzVmc2yHFfGFd7A6VKAVuNodFejRAzonHR ba12zviAfZIxKUUVk2REP012rA== X-Google-Smtp-Source: ABdhPJwIjq9lYuQhM3FH2gc+pxAdwAiYrs0l12AOk5fB9VWB2KLk0fYkbyVNblL9BUDJu5BmwUnnmQ== X-Received: by 2002:a17:90a:6345:: with SMTP id v5mr15940089pjs.17.1626121255710; Mon, 12 Jul 2021 13:20:55 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id a9sm16277331pfo.69.2021.07.12.13.20.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jul 2021 13:20:55 -0700 (PDT) Date: Mon, 12 Jul 2021 20:20:51 +0000 From: Sean Christopherson To: David Matlack Cc: Ben Gardon , kvm , Joerg Roedel , Jim Mattson , Wanpeng Li , Vitaly Kuznetsov , Paolo Bonzini , Junaid Shahid , Andrew Jones , Matthew Wilcox , Yu Zhao , David Hildenbrand , Andrew Morton Subject: Re: [PATCH v2 3/6] KVM: x86/mmu: Make walk_shadow_page_lockless_{begin,end} interoperate with the TDP MMU Message-ID: References: <20210630214802.1902448-1-dmatlack@google.com> <20210630214802.1902448-4-dmatlack@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jul 12, 2021, David Matlack wrote: > On Mon, Jul 12, 2021 at 10:02:31AM -0700, Ben Gardon wrote: > > On Wed, Jun 30, 2021 at 2:48 PM David Matlack wrote: > > > > > > Acquire the RCU read lock in walk_shadow_page_lockless_begin and release > > > it in walk_shadow_page_lockless_end when the TDP MMU is enabled. This > > > should not introduce any functional changes but is used in the following > > > commit to make fast_page_fault interoperate with the TDP MMU. > > > > > > Signed-off-by: David Matlack > > > > Reviewed-by: Ben Gardon > > > > This as I understand this, we're just lifting the rcu_lock/unlock out > > of kvm_tdp_mmu_get_walk, and then putting all the TDP MMU specific > > stuff down a level under walk_shadow_page_lockless_begin/end and > > get_walk. > > > > Instead of moving kvm_tdp_mmu_get_walk_lockless into get_walk, it > > could also be open-coded as: > > > > walk_shadow_page_lockless_begin > > if (is_tdp_mmu(vcpu->arch.mmu)) > > leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root); > > else > > leaf = get_walk(vcpu, addr, sptes, &root); > > walk_shadow_page_lockless_end > > > > in get_mmio_spte, since get_walk isn't used anywhere else. Then > > walk_shadow_page_lockless_begin/end could also be moved up out of > > get_walk instead of having to add a goto to that function. > > I don't have a strong preference either way, but the above feels like > > a slightly simpler refactor. > > I don't have a strong preference either way as well. I'd be happy to > switch to your suggestion in v3. I vote for Ben's suggestion. As is, I think it would be too easy to overlook the TDP MMU path in get_walk() and focus only on the for-loop.