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=-0.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 1A732C352A1 for ; Sat, 8 Feb 2020 00:18:47 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 8E47C206CC for ; Sat, 8 Feb 2020 00:18:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YLM/AWYW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E47C206CC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E8D5C4A54B; Fri, 7 Feb 2020 19:18:45 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@redhat.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jJnCvDU1Ccuv; Fri, 7 Feb 2020 19:18:44 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 05A2A4A551; Fri, 7 Feb 2020 19:18:44 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 462D54A542 for ; Fri, 7 Feb 2020 19:18:43 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id NySIJWZOzz+F for ; Fri, 7 Feb 2020 19:18:42 -0500 (EST) Received: from us-smtp-delivery-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 22F124A535 for ; Fri, 7 Feb 2020 19:18:42 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581121121; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=LFIEzo7uypY+04BO5xYReIB8V2LuQNl/7zA6bw0w6C4=; b=YLM/AWYW0Ae0Bbu5V4My8wNJvDcWNF/0olu8pjss4IFWE9QqS5yUCD9CmDAn0Xz61V4F1k PuwFswNcaTk29a2ov57pUzEuvoq2e+gLUSyWYtz6wnkUE7WZkxIvrstfiTEloh22zFQqO4 l8V9ee8zJW/XklRKtnQfXM80RaEDFKc= Received: from mail-qt1-f199.google.com (mail-qt1-f199.google.com [209.85.160.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-158-hm1gKe1vN0mvxFx_A_MdAw-1; Fri, 07 Feb 2020 19:18:37 -0500 Received: by mail-qt1-f199.google.com with SMTP id t4so688286qtd.3 for ; Fri, 07 Feb 2020 16:18:37 -0800 (PST) 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=FliTqS6db2UW8mSq2D177P6p0LFTqK9NtxjpkxKtGhE=; b=Rl9qBdTPWKJdaEIsg9EKJxaldWe+I/tUf0wLjeo3qZhJHAr6xylLpriY81a3x7I/KF BNYrJcE7XOhQLtd4ZESN66dDLoLwgzYeio2y/4SEy3Qz4C+N9WwkfJi6jXJiccTKS/EQ ysYdKUNEM6H41kGZ1RhMV1oq/+5sbCbJD++/aIkJF6s9MzgKMLrvvAjcnfw9PpYpD00R itAKLZzveYPCjz6AFT4YS3E0UA4SE3UCuqVLRHQCW0RLRL1gZ9oEllh9eH0s2RUnVpOt e+bDqtuhjOyrQBJGPypg81XcnB3UbR8RmvL6K3Kd/Jejee1Oi5RYLJabiSIxNu42oBv7 vhfw== X-Gm-Message-State: APjAAAW3v01rBwdiYezSTEKpXxzD4Zo63ZdXsGAzkTylib0ilVwYbMY9 eqUkxeOzbIX4xec7gdAl6VY6B1P+jJSHuJFbIx9LuUpENTINZ0yEBGMKW6L395I0Vj6Gjp22ZWt orAzZ+cEsabArTRb6spTXMnZG X-Received: by 2002:a37:8cc:: with SMTP id 195mr1462273qki.456.1581121117034; Fri, 07 Feb 2020 16:18:37 -0800 (PST) X-Google-Smtp-Source: APXvYqzAkXLXCBlBGfr3jniMMbcCpWv44CMlkznbhHCioVsTu+8iTId/2cuSvhY/ok33KerrRsEvMw== X-Received: by 2002:a37:8cc:: with SMTP id 195mr1462239qki.456.1581121116707; Fri, 07 Feb 2020 16:18:36 -0800 (PST) Received: from xz-x1 ([2607:9880:19c8:32::2]) by smtp.gmail.com with ESMTPSA id n32sm2271790qtk.66.2020.02.07.16.18.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Feb 2020 16:18:35 -0800 (PST) Date: Fri, 7 Feb 2020 19:18:32 -0500 From: Peter Xu To: Sean Christopherson Subject: Re: [PATCH v5 15/19] KVM: Provide common implementation for generic dirty log functions Message-ID: <20200208001832.GA823968@xz-x1> References: <20200121223157.15263-1-sean.j.christopherson@intel.com> <20200121223157.15263-16-sean.j.christopherson@intel.com> <20200206200200.GC700495@xz-x1> <20200206212120.GF13067@linux.intel.com> <20200206214106.GG700495@xz-x1> <20200207194532.GK2401@linux.intel.com> MIME-Version: 1.0 In-Reply-To: <20200207194532.GK2401@linux.intel.com> X-MC-Unique: hm1gKe1vN0mvxFx_A_MdAw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Wanpeng Li , kvm@vger.kernel.org, David Hildenbrand , linux-mips@vger.kernel.org, Paul Mackerras , kvmarm@lists.cs.columbia.edu, Janosch Frank , Marc Zyngier , Joerg Roedel , Christian Borntraeger , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jim Mattson , Cornelia Huck , linux-kernel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Fri, Feb 07, 2020 at 11:45:32AM -0800, Sean Christopherson wrote: > +Vitaly for HyperV > > On Thu, Feb 06, 2020 at 04:41:06PM -0500, Peter Xu wrote: > > On Thu, Feb 06, 2020 at 01:21:20PM -0800, Sean Christopherson wrote: > > > On Thu, Feb 06, 2020 at 03:02:00PM -0500, Peter Xu wrote: > > > > But that matters to this patch because if MIPS can use > > > > kvm_flush_remote_tlbs(), then we probably don't need this > > > > arch-specific hook any more and we can directly call > > > > kvm_flush_remote_tlbs() after sync dirty log when flush==true. > > > > > > Ya, the asid_flush_mask in kvm_vz_flush_shadow_all() is the only thing > > > that prevents calling kvm_flush_remote_tlbs() directly, but I have no > > > clue as to the important of that code. > > > > As said above I think the x86 lockdep is really not necessary, then > > considering MIPS could be the only one that will use the new hook > > introduced in this patch... Shall we figure that out first? > > So I prepped a follow-up patch to make kvm_arch_dirty_log_tlb_flush() a > MIPS-only hook and use kvm_flush_remote_tlbs() directly for arm and x86, > but then I realized x86 *has* a hook to do a precise remote TLB flush. > There's even an existing kvm_flush_remote_tlbs_with_address() call on a > memslot, i.e. this exact scenario. So arguably, x86 should be using the > more precise flush and should keep kvm_arch_dirty_log_tlb_flush(). > > But, the hook is only used when KVM is running as an L1 on top of HyperV, > and I assume dirty logging isn't used much, if at all, for L1 KVM on > HyperV? > > I see three options: > > 1. Make kvm_arch_dirty_log_tlb_flush() MIPS-only and call > kvm_flush_remote_tlbs() directly for arm and x86. Add comments to > explain when an arch should implement kvm_arch_dirty_log_tlb_flush(). > > 2. Change x86 to use kvm_flush_remote_tlbs_with_address() when flushing > a memslot after the dirty log is grabbed by userspace. > > 3. Keep the resulting code as is, but add a comment in x86's > kvm_arch_dirty_log_tlb_flush() to explain why it uses > kvm_flush_remote_tlbs() instead of the with_address() variant. > > I strongly prefer to (2) or (3), but I'll defer to Vitaly as to which of > those is preferable. > > I don't like (1) because (a) it requires more lines code (well comments), > to explain why kvm_flush_remote_tlbs() is the default, and (b) it would > require even more comments, which would be x86-specific in generic KVM, > to explain why x86 doesn't use its with_address() flush, or we'd lost that > info altogether. > I proposed the 4th solution here: https://lore.kernel.org/kvm/20200207223520.735523-1-peterx@redhat.com/ I'm not sure whether that's acceptable, but if it can, then we can drop the kvm_arch_dirty_log_tlb_flush() hook, or even move on to per-slot tlb flushing. Thanks, -- Peter Xu _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm