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 B28BCC433F5 for ; Tue, 11 Jan 2022 10:23:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237686AbiAKKXx (ORCPT ); Tue, 11 Jan 2022 05:23:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233911AbiAKKXw (ORCPT ); Tue, 11 Jan 2022 05:23:52 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6E4EC06173F for ; Tue, 11 Jan 2022 02:23:51 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 587DBB819D0 for ; Tue, 11 Jan 2022 10:23:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0D6E5C36AE9; Tue, 11 Jan 2022 10:23:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1641896629; bh=rLjD10oD9rqTVqIwpiJZNWSMQasAD9/0XTaE7F0fPJM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=TCU5mDKO7IVKoA6t1LM1XXUwtnRWErJZiM8V0rm9W6W0dOtlo41/6ao7AGeXG6DWo a3CxPbUcMDKNUwEY98ghskIzMQPGU7aODjowexlxLse7uqek8kjj9w1eVbJMObl7ji LoFBKsAtgbNkMqkZa3s6WlU4x0cuTdHeuSFSipv1kCrt9Un4m5uAyE75Rao/HMaypl 1gkfZz2BzJRRtkUwMKw4ZCHSn0dnLIDFvx5UObh7bUWcBzYA3e1wMP4/kKZeY6wuVz hCIenB7SZQHvNn7XAZ6T9+r+cPcFA+bnHnurRrlsYdfgYWHb7NOWIlY6Ubun7FPivZ SZHKTUH9gOKFw== Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1n7EJf-00HM32-2U; Tue, 11 Jan 2022 10:23:47 +0000 Date: Tue, 11 Jan 2022 10:23:46 +0000 Message-ID: <87bl0itvt9.wl-maz@kernel.org> From: Marc Zyngier To: Jing Zhang Cc: KVM , KVMARM , Will Deacon , Paolo Bonzini , David Matlack , Oliver Upton , Reiji Watanabe Subject: Re: [RFC PATCH 1/3] KVM: arm64: Use read/write spin lock for MMU protection In-Reply-To: <20220110210441.2074798-2-jingzhangos@google.com> References: <20220110210441.2074798-1-jingzhangos@google.com> <20220110210441.2074798-2-jingzhangos@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: jingzhangos@google.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, will@kernel.org, pbonzini@redhat.com, dmatlack@google.com, oupton@google.com, reijiw@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, 10 Jan 2022 21:04:39 +0000, Jing Zhang wrote: > > To reduce the contentions caused by MMU lock, some MMU operations can > be performed under read lock. > One improvement is to add a fast path for permission relaxation during > dirty logging under the read lock. This commit message really doesn't say what this patch does (converting our MMU spinlock to a rwlock, and replacing all instances of the lock being acquired with a write lock acquisition). Crucially, it only mention the read lock which appears *nowhere* in this patch. Thanks, M. -- Without deviation from the norm, progress is not possible.