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=-0.6 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 4DD85C34022 for ; Mon, 17 Feb 2020 15:45:20 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id CFB8C22B48 for ; Mon, 17 Feb 2020 15:45:19 +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="DiycSGBG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CFB8C22B48 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 431764AF4C; Mon, 17 Feb 2020 10:45:19 -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 EPvixeF6yiXj; Mon, 17 Feb 2020 10:45:18 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 346364AF56; Mon, 17 Feb 2020 10:45:18 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 5D2C24AF4C for ; Mon, 17 Feb 2020 10:35:14 -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 VHcbBk2mJZOG for ; Mon, 17 Feb 2020 10:35:13 -0500 (EST) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 423214AF29 for ; Mon, 17 Feb 2020 10:35:13 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581953713; 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=f9k/lECSipAyKMEJyCYwRMAHJ7XyYrMgRJSZNNqcEog=; b=DiycSGBG4J1DVnf//UzqX9H9/eFQDkXhtrA47xybpfHnzCZVN766tj095TaHGsEWh/cBTu 2UD3ojFbJT2TTsubkoKLoYCuz4I2us2oifgjevvpXuAHj0cP87zf1BBzDRsyVMfeexpvy/ ex8beoivXAc54D1ChPlZM+9vP+yZ2Cw= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-184-PDsMg9KsPuGeYn4K_fNkhw-1; Mon, 17 Feb 2020 10:35:08 -0500 Received: by mail-wr1-f70.google.com with SMTP id n23so9109783wra.20 for ; Mon, 17 Feb 2020 07:35:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=I94s+/OW2nmFtGVziJ+53lmgRDQEQNRHpvcvNRvPjFg=; b=okVhWe4OtcIalLKfbivTFdge+X6yLvc3PCnIL2l3tijEEnd7T8opKmo8PY714WhI3w iozbLKaEQ6+y8kUsU1rTvgxuvZiR5ff9Q907D/qzzCwyM+C6Y7OrJEezljeyR/0XUxBC AdikS8RNj0h7Y9zccA8WJkDbnQ2WfsHw468wmmb4gaEvLzmkK1b860oLCThS3frvy29f GnS1gQ7CElFjgaBhFzEKdlDU9r87/MGms8fEqC8CzPPO47sea2/nvvvd4GhxP1gC/f5L XSaeJuxTDL2ojMQPMIoyjyJ28p16ghodQR/NB1NjbDQrLRWGIYxx4k+msS8jeV6R100q BHMA== X-Gm-Message-State: APjAAAWBYooapmGbUJ9M5NOlB+7w8xMq6qm85bJjKm7refjrY6YjAXX0 KBcGxs6Wb95tGQHahq3vLTPxgQM5EOAKgM6v5H0dYaJqO+3j2Ek8ezR1KIQRPMNDE5s4QPRfwEx 3r8DsL+kFiU8ht86gJs5BxJin X-Received: by 2002:a7b:cd8e:: with SMTP id y14mr22883677wmj.150.1581953707731; Mon, 17 Feb 2020 07:35:07 -0800 (PST) X-Google-Smtp-Source: APXvYqw70CrrrSfMwVWl7qnn5bAkrGx2tWvnt4qyiyI0/zrMUKDzlnUG9J1tN9btzikV0/JwRnl8xw== X-Received: by 2002:a7b:cd8e:: with SMTP id y14mr22883657wmj.150.1581953707447; Mon, 17 Feb 2020 07:35:07 -0800 (PST) Received: from vitty.brq.redhat.com (nat-pool-brq-t.redhat.com. [213.175.37.10]) by smtp.gmail.com with ESMTPSA id y8sm1018221wma.10.2020.02.17.07.35.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Feb 2020 07:35:06 -0800 (PST) From: Vitaly Kuznetsov To: Sean Christopherson , Peter Xu Subject: Re: [PATCH v5 15/19] KVM: Provide common implementation for generic dirty log functions In-Reply-To: <20200207194532.GK2401@linux.intel.com> 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> Date: Mon, 17 Feb 2020 16:35:05 +0100 Message-ID: <87v9o59qhi.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 X-MC-Unique: PDsMg9KsPuGeYn4K_fNkhw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Mailman-Approved-At: Mon, 17 Feb 2020 10:45:16 -0500 Cc: Wanpeng Li , Janosch Frank , kvm@vger.kernel.org, David Hildenbrand , Marc Zyngier , Joerg Roedel , Cornelia Huck , linux-mips@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras , Christian Borntraeger , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , linux-arm-kernel@lists.infradead.org, Paolo Bonzini , kvmarm@lists.cs.columbia.edu, Jim Mattson 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 Sean Christopherson writes: > +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? (Sorry for the delayed reply, was traveling last week) When KVM runs as an L1 on top of Hyper-V it uses eVMCS by default and eVMCSv1 doesn't support PML. I've also just checked Hyper-V 2019 and it hides SECONDARY_EXEC_ENABLE_PML from guests (this was expected). > > 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'd vote for (2): while this will effectively be kvm_flush_remote_tlbs() for now, we may think of something smarter in the future (e.g. PV interface for KVM-on-KVM). > > 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. > -- Vitaly _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm