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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 81DC9C2BA83 for ; Fri, 7 Feb 2020 19:45:53 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 58A1420726 for ; Fri, 7 Feb 2020 19:45:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="VlSDfgZJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 58A1420726 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jsDsGOIMDzeW+Rwgl++Ase7k9nCpDR1x86d1ia8QLwA=; b=VlSDfgZJSNxHRx jjQV3eh4xkX9oNv8fCEPMXhR7Teo263ubtXFroen/woBQboI+1/FRNoqJilbzS9AZhWBV6gG81Q5A 7QFiRH4TO1cRDvlVafd0ugUsPZ2dXiaq+1mEe3jjmjJMU+4i/DOyx10mG2suCbL/1gu/RYNkSgM4i siqTThwm9f5uyOHdO/YdJxOki+b7bqzE3ohrMWNQXOdKjPkCevfNTkjQOd1Zn7enzsZQsXri/I8sy 6erPQN+/LQwAmQlq0O7sflJELZsCsccKt20F7i59sm6nMRIx/D4xKatv5SA/3BGLYeTyiKh74f9EA m6WQQhE3W3x5HkVn68iQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j09ZO-00067K-GV; Fri, 07 Feb 2020 19:45:42 +0000 Received: from mga03.intel.com ([134.134.136.65]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1j09ZL-00066H-Pi for linux-arm-kernel@lists.infradead.org; Fri, 07 Feb 2020 19:45:41 +0000 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Feb 2020 11:45:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,414,1574150400"; d="scan'208";a="312123734" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by orsmga001.jf.intel.com with ESMTP; 07 Feb 2020 11:45:32 -0800 Date: Fri, 7 Feb 2020 11:45:32 -0800 From: Sean Christopherson To: Peter Xu , Vitaly Kuznetsov Subject: Re: [PATCH v5 15/19] KVM: Provide common implementation for generic dirty log functions Message-ID: <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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200206214106.GG700495@xz-x1> User-Agent: Mutt/1.5.24 (2015-08-30) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200207_114539_918090_9C9B1870 X-CRM114-Status: GOOD ( 16.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 , Julien Thierry , Suzuki K Poulose , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jim Mattson , Cornelia Huck , Christoffer Dall , linux-kernel@vger.kernel.org, James Morse , Paolo Bonzini , Vitaly Kuznetsov , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org +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. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel