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 865A8C433EF for ; Tue, 19 Jul 2022 22:43:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240205AbiGSWnD (ORCPT ); Tue, 19 Jul 2022 18:43:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236742AbiGSWnB (ORCPT ); Tue, 19 Jul 2022 18:43:01 -0400 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE4B8509F7 for ; Tue, 19 Jul 2022 15:43:00 -0700 (PDT) Received: by mail-pl1-x62b.google.com with SMTP id q5so13300619plr.11 for ; Tue, 19 Jul 2022 15:43:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=3mBMNTNhashQoUW+48e8V6j0bFm9Antzk3St87vtHyQ=; b=sbILa/KKpaY/yaJBO8yP6X5Tf3PfNDgbJK2WWJHf09SLNUW9sePi5k4LtP7CecLnZF z8fHFi8S7PTaNe1ny88KxX7bgthd9DzxzNmusdUgsJgPP/AJMFV9y2lG7kp4kZsbr47c C1j/haDut2mgx72jxqeWBejL/dW7ib+P+TQ8RxkzsgqM/QDGaRtAOa1rSXd2azdEeXfY Yx5RwTeDcj3fk0AQNkcXqwv7sQbaDnWD1HwtoW6p0CRh95uq5d3mrTX4G+1xmXdSA9wa r+fj/ruXM3x1yjXDQ+/Gp6K+jMJ4MhxMx7v1rCIFwt8AW1HrE2IRLHkMhITdo/QMOV2/ YiLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=3mBMNTNhashQoUW+48e8V6j0bFm9Antzk3St87vtHyQ=; b=LD3m8ZEQomYH0urs++iR6aYJq58sohiEsa/3U/Y8kAYVjz1tyIzk9PYS6u8Bxrch5S Cs7pxcvF+Es38F9hWV22jKCEaTOLjZpUCSOpql0BHKKyxQBI86r1kCdv8dpJZ3GLNVji Dm0JNknWXK+5EIcMOZTbt4p4SCwjyGzZFXfB9z9UeMPUq1klgeGxBr2OpYa3Oj9SX2sP fl7K0oalbbzZI2MKiv0jBOVQKucDq9mQ5kNKMRIvOzWd5bNTUPF5A+XcLkJMkg+gjRk2 j3FOX3Q0ZIZuE7zOE05801oEG3fd/lPcygqX6RzXKyuh/47QSSBb1LCJsQt2Q64+M+Vb gNuQ== X-Gm-Message-State: AJIora+hmTNH+qiu7iCp+UTW2P/bUrh619vgkwaJ8KOZno0koOg6auTe aKfwUiFUoh4gMR7QHxcyBi3z4eW1pIPlwA== X-Google-Smtp-Source: AGRyM1vPLoWkMbH196Cy88DSN5XsqMQVREA4QruekZ7i34VY83xVjisjTYv51mdZYk9VzlutlXr9Jg== X-Received: by 2002:a17:90b:1b42:b0:1f0:447f:995c with SMTP id nv2-20020a17090b1b4200b001f0447f995cmr1791428pjb.200.1658270580349; Tue, 19 Jul 2022 15:43:00 -0700 (PDT) Received: from google.com (123.65.230.35.bc.googleusercontent.com. [35.230.65.123]) by smtp.gmail.com with ESMTPSA id y36-20020a634b24000000b0040cfb5151fcsm10496778pga.74.2022.07.19.15.42.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jul 2022 15:43:00 -0700 (PDT) Date: Tue, 19 Jul 2022 22:42:56 +0000 From: Sean Christopherson To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Maxim Levitsky , David Matlack , Lai Jiangshan Subject: Re: [PATCH V3 07/12] KVM: X86/MMU: Remove the check of the return value of to_shadow_page() Message-ID: References: <20220521131700.3661-1-jiangshanlai@gmail.com> <20220521131700.3661-8-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220521131700.3661-8-jiangshanlai@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 21, 2022, Lai Jiangshan wrote: > From: Lai Jiangshan > > Remove the check of the return value of to_shadow_page() in > mmu_free_root_page(), kvm_mmu_free_guest_mode_roots(), is_unsync_root() > and is_tdp_mmu() because it can not return NULL. s/can not/can no longer, to make it very clear the to_shadow_page() _could_ return NULL in the past, but something changed. And please explain _why_ it can no longer return NULL, even if that's just a reference to kvm_mmu_alloc_local_shadow_page() or whatever it ends up being named. That can also tie into the obsolete sp handling. > Remove the check of the return value of to_shadow_page() in > is_page_fault_stale() and is_obsolete_root() because it can not return > NULL and the obsoleting for local shadow page is already handled by > a different way. > > When the obsoleting process is done, all the obsoleted non-local shadow > pages are already unlinked from the local shadow pages by the help of > the parent rmap from the children and the local shadow pages become > theoretically valid again. The local shadow page can be freed if > is_obsolete_sp() return true, or be reused if is_obsolete_sp() becomes > false. > > Reviewed-by: David Matlack > Signed-off-by: Lai Jiangshan > ---