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 983F5C4332F for ; Sat, 12 Nov 2022 00:43:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234602AbiKLAnO (ORCPT ); Fri, 11 Nov 2022 19:43:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51520 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233911AbiKLAnN (ORCPT ); Fri, 11 Nov 2022 19:43:13 -0500 Received: from mail-pf1-x42f.google.com (mail-pf1-x42f.google.com [IPv6:2607:f8b0:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D9D976FBA for ; Fri, 11 Nov 2022 16:43:12 -0800 (PST) Received: by mail-pf1-x42f.google.com with SMTP id z26so6232500pff.1 for ; Fri, 11 Nov 2022 16:43:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=W/69SGTblteqzTGqi+tKsPG0LW4tOtiDqnrFyQWptaQ=; b=nkkHJRYG9RSNUubkLNubrJI/d3KOEidZrgmUPThr3GFsr7fra6VsI+pb1qqQQ02WKX zF1WmMPVXJP4zWYv5H2yrK2XmJWXLyIYGleBrctfrNS+0hqbbCZ/iqh9/fdMvnZajEwa S7yTODLsbBcMwXwbemvi9xcCSHrHJ12nb+aTQowsorgnzkj19FB9Krp7KBYJxZyP21EO 7pIoX7pjC6wc+oSETXDUqR/kq2X+LicMr3aKFzkyce/50iVQxoQgCThUjuJ/3KLMl8+B z6LnADkM+0e/zYQoLtoBvelqEGFYq3NJyiIEmKpY5AR6UOQqXPItQJPmeuPg0YF/+hoh Qb/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=W/69SGTblteqzTGqi+tKsPG0LW4tOtiDqnrFyQWptaQ=; b=4ZklvRWuxpIfLTWcI/aTziLZ+xRJnIp0ass0IVYygRh82cG3vBFC2dRZg8mMHhaebF 1duse+QwXMpO0xL0u9e6ObXVsqa/AXD9qnhGriWh1Lc0PoBnCAE1XId9r3jqXaCk1J0E H335hyrVHn497ZYGvh+etTNCL+c03ICe9SoF5nWzCq4lk+eWcF39twdQ+1rLY6au00WC SRtZO/tjIxEUTwayleI8hVJLIv5pIDIJIB4x214xqpdzAlVvXcTCeZIXS9n4z7ZL2Z7w HkUl60F5CNdNyxC93bnhAS5VxIpmc21J79hemeUTmWjv9QQsQyWFL4EHZj9DpAob2pER DLbQ== X-Gm-Message-State: ANoB5pl6AFVGwo9EceFEImNiSl1v8XvOD3LH+z8dM5Gg9XdL24hg0Yr+ 7VpdlpO21S6VGIJgzNIk6MvAEhxE32y25w== X-Google-Smtp-Source: AA0mqf4WsOfrQhaQruL4asl5Iu86noh/aH6GkJDdmp/AzA4oKTD7iRzggslPFH8j54SEF3nTst7kQA== X-Received: by 2002:a62:838f:0:b0:56c:8b7:f2dc with SMTP id h137-20020a62838f000000b0056c08b7f2dcmr5095877pfe.16.1668213791697; Fri, 11 Nov 2022 16:43:11 -0800 (PST) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id o127-20020a625a85000000b0056bc9294e1asm2154927pfb.24.2022.11.11.16.43.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Nov 2022 16:43:11 -0800 (PST) Date: Sat, 12 Nov 2022 00:43:07 +0000 From: Sean Christopherson To: Yan Zhao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, intel-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, zhenyuw@linux.intel.com Subject: Re: [PATCH v2 1/3] KVM: x86: add a new page track hook track_remove_slot Message-ID: References: <20221111103247.22275-1-yan.y.zhao@intel.com> <20221111103350.22326-1-yan.y.zhao@intel.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 Sat, Nov 12, 2022, Yan Zhao wrote: > And I'm also not sure if a slots_arch_lock is required for > kvm_slot_page_track_add_page() and kvm_slot_page_track_remove_page(). It's not required. slots_arch_lock protects interaction between memslot updates mmu_first_shadow_root_alloc(). When CONFIG_KVM_EXTERNAL_WRITE_TRACKING=y, then the mmu_first_shadow_root_alloc() doesn't touch the memslots because everything is pre-allocated: bool kvm_page_track_write_tracking_enabled(struct kvm *kvm) { return IS_ENABLED(CONFIG_KVM_EXTERNAL_WRITE_TRACKING) || !tdp_enabled || kvm_shadow_root_allocated(kvm); } int kvm_page_track_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned long npages) { if (!kvm_page_track_write_tracking_enabled(kvm)) <== always true return 0; return __kvm_page_track_write_tracking_alloc(slot, npages); } Though now that you point it out, it's tempting to #ifdef out some of those hooks so that's basically impossible for mmu_first_shadow_root_alloc() to cause problems. Not sure the extra #ideffery would be worth while though. slots_arch_lock also protects shadow_root_allocated, but that's a KVM-internal detail that isn't relevant to the page-tracking machinery when CONFIG_KVM_EXTERNAL_WRITE_TRACKING=y.