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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 3E02DC61DA4 for ; Mon, 13 Mar 2023 10:11:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc: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=0o/Tf5m4wJL7KnN859FHJicJv2uxVlNn2U27xmNtySw=; b=DXerTa5wT68jWL CK9R12IpoczQ5U0rhXn3t0OryTiZhneUiVXtnkbsypYx7FnZyDC80+Uu+i5OAMYx4+6J16D9iAPu2 EMmW7vyE+RmZb2vhNYFrgYvdywE1uqxm5BSkiT0z818vQ5qFOBa7lfGuIuLopjd/EUXR0S2tuSMvM IYbKmY5Xyku/xFW682kPBru8ceRZa3Stj0taxr1f6nTwmkBtFMkGOsm+N0n7CIT/Gnp2VyK1IXtaF vn8v+UrJpofFpcFVixWDpxdZpwdd4vIBSnLGaqiEAHCMkFKAKrHLr8E67ke2uxEekIJ0uliCdvzQ9 S6G0lOnqas+qVk0yYCYg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pbf8C-0057OO-2g; Mon, 13 Mar 2023 10:10:16 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pbf85-0057Ly-8d for linux-arm-kernel@lists.infradead.org; Mon, 13 Mar 2023 10:10:13 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E200C2F4; Mon, 13 Mar 2023 03:10:46 -0700 (PDT) Received: from e120937-lin (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 228E03F71A; Mon, 13 Mar 2023 03:10:02 -0700 (PDT) Date: Mon, 13 Mar 2023 10:09:55 +0000 From: Cristian Marussi To: Oliver Upton Cc: Jeremy Linton , "linux-arm-kernel@lists.infradead.org" , kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, "linux-kernel@vger.kernel.org" , David Woodhouse , Marc Zyngier Subject: Re: Circular lockdep in kvm_reset_vcpu() ? Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230313_031009_395333_F29D49B4 X-CRM114-Status: GOOD ( 18.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Feb 11, 2023 at 12:56:41AM +0000, Oliver Upton wrote: > Hi Jeremy, > Hi, > On Fri, Feb 10, 2023 at 11:46:36AM -0600, Jeremy Linton wrote: > > Hi, > > > > I saw this pop yesterday: > > You and me both actually! Shame on me, I spoke off-list about this with > Marc in passing. Thanks for sending along the report. > > > [ 78.333360] ====================================================== > > [ 78.339541] WARNING: possible circular locking dependency detected > > [ 78.345721] 6.2.0-rc7+ #19 Not tainted > > [ 78.349470] ------------------------------------------------------ > > [ 78.355647] qemu-system-aar/859 is trying to acquire lock: > > [ 78.361130] ffff5aa69269eba0 (&host_kvm->lock){+.+.}-{3:3}, at: > > kvm_reset_vcpu+0x34/0x274 > > [ 78.369344] > > [ 78.369344] but task is already holding lock: > > [ 78.375182] ffff5aa68768c0b8 (&vcpu->mutex){+.+.}-{3:3}, at: > > kvm_vcpu_ioctl+0x8c/0xba0 > > [...] > > > It appears to be triggered by the new commit 42a90008f890a ('KVM: Ensure > > lockdep knows about kvm->lock vs. vcpu->mutex ordering rule') which is > > detecting the vcpu lock grabbed by kvm_vcpu_ioctl() and then the kvm mutext > > grabbed by kvm_reset_vcpu(). > > Right, this commit gave lockdep what it needed to smack us on the head > for getting the locking wrong in the arm64 side. > > As gross as it might be, the right direction is likely to have our own > lock in kvm_arch that we can acquire while holding the vcpu mutex. I'll > throw a patch at the list once I get done testing it. > I just hit this using a v6.3-rc2 and a mainline kvmtool. In my case, though, the guest does not even boot if I use more than 1 vcpu, which I suppose triggers effectively the reported possible deadlock, i.e.: root/lkvm_master run -c 4 -m 4096 -k /root/Image_guest -d /root/disk_debian_buster_guest.img -p "loglevel=8" # lkvm run -k /root/Image_guest -m 4096 -c 4 --name guest-288 .... Thanks, Cristian _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel