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 15588C32772 for ; Tue, 23 Aug 2022 09:39:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351404AbiHWJj3 (ORCPT ); Tue, 23 Aug 2022 05:39:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351505AbiHWJik (ORCPT ); Tue, 23 Aug 2022 05:38:40 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F30C5F9BC; Tue, 23 Aug 2022 01:40:52 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id e19so12193157pju.1; Tue, 23 Aug 2022 01:40:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc; bh=BjyTp1rYXZbh0tG3MYfP1QG1fJZgUbfQ/sbIoo651Uo=; b=HfohDmdWLWKSq9YTwl/9HcIjQ9n+PpwN9SG+tgxAKvwcdnDOaUmbnpsPXomnO8pDbQ jvvh+MxiSNkiupFmYdS8P9u7hLDB9h2j4CKJm0hlx6k9K1NUogQ5S5mElTOIA21veSN4 NIZ/7iWsMluW2jJm3UX/BtK4T8TYEYuAxwUNU8gxdjn+6RUrrMb4A7RM1mxTV/q4AK61 6tM2NUbuYhq/NnMbl6h6cugoCGeoE65SorFq+eDb7tDlXlcHcVn5RKnEkgVPFV6dkGl9 X9z8ZDtWhiZfPatTbCtCA8VYuMDrEnLjn6koUJVw56JaWnT7Cq44tygpTZ6NuS0OFtOH U1wQ== 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; bh=BjyTp1rYXZbh0tG3MYfP1QG1fJZgUbfQ/sbIoo651Uo=; b=cGvR/1B5X5VdP9M3LNlQ6p26EuNaNwk5DU/C1drqstxWm08AI7EvfttDNQvgEmB1/t JhF/3E082mCcZ99uZRhcHweZsnLKZ2dkExKSfNQjguo1LD8Hw9p/attkIcxAjSwFTIcK yaGO5DKnCVKi6ctpA24xmxbn7yP0QSD3XJ9/c8PdpaxyJ38OFOdrSNGexhCPRTlSUI0l 8GqLvW5OKDcTqtlhm4biDguJjmPYfFUkyGH/QUaVERJLZbbrRIRvpKjKYwE3Qcxd9Dzh XmYeFO/+T2wpGGBh2X3NkAc45S/0UNP9/9jC65MaCWv5s2f7MPrkS9aPeE6YYrKn2WFP zIIQ== X-Gm-Message-State: ACgBeo0dnBl3+NfMlsYq/c6YFPfK7qLOTD5TD/m1rTcgDa5TKEDqSbWC +Y311LOAmPXVM6vJI2DRp4I= X-Google-Smtp-Source: AA6agR7bqHHDTFsoQJM3fNgJxY16Za603VCMAuEoJ2sYDxB9TB6siix6ySC1b7udrSjQA7v1iONuDw== X-Received: by 2002:a17:90b:1bd1:b0:1fb:5640:ffa4 with SMTP id oa17-20020a17090b1bd100b001fb5640ffa4mr2212440pjb.220.1661244005306; Tue, 23 Aug 2022 01:40:05 -0700 (PDT) Received: from localhost ([192.55.55.51]) by smtp.gmail.com with ESMTPSA id k17-20020a170902c41100b001709b9d292esm10001850plk.268.2022.08.23.01.40.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 01:40:04 -0700 (PDT) Date: Tue, 23 Aug 2022 01:40:03 -0700 From: Isaku Yamahata To: Chao Gao Cc: isaku.yamahata@intel.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com, Paolo Bonzini , Sean Christopherson , Kai Huang , Will Deacon Subject: Re: [RFC PATCH 03/18] KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock Message-ID: <20220823084003.GF2147148@ls.amr.corp.intel.com> References: <6b07c02dd361f834fea442eb8dae53f23618f983.1660974106.git.isaku.yamahata@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Aug 23, 2022 at 10:26:09AM +0800, Chao Gao wrote: > On Fri, Aug 19, 2022 at 11:00:09PM -0700, isaku.yamahata@intel.com wrote: > >From: Isaku Yamahata > > > >Because kvm_count_lock unnecessarily complicates the KVM locking convention > >Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock for > >simplicity. > > > >Opportunistically add some comments on locking. > > > >Suggested-by: Sean Christopherson > >Signed-off-by: Isaku Yamahata > >--- > > static cpumask_var_t cpus_hardware_enabled; > >@@ -4999,6 +4998,8 @@ static void hardware_enable_nolock(void *junk) > > int cpu = raw_smp_processor_id(); > > int r; > > > >+ WARN_ON_ONCE(preemptible()); > >+ > > if (cpumask_test_cpu(cpu, cpus_hardware_enabled)) > > return; > > > >@@ -5015,10 +5016,10 @@ static void hardware_enable_nolock(void *junk) > > > > static int kvm_starting_cpu(unsigned int cpu) > > { > >- raw_spin_lock(&kvm_count_lock); > >+ mutex_lock(&kvm_lock); > > kvm_starting_cpu() is called with interrupt disabled. So we cannot use > sleeping locks (e.g., mutex) here. So your patch to move it to online section [1] is needed. I thought I can pullin only some of your patches. But whole your patches are needed. [1] https://lore.kernel.org/lkml/20220317091539.GA7257@gao-cwp/T/#mcc0fd81e7a19601e7c3ce451582c516d38f977f6 -- Isaku Yamahata