From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from r3-18.sinamail.sina.com.cn (r3-18.sinamail.sina.com.cn [202.108.3.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5D7DF4CCDE5 for ; Fri, 4 Sep 2026 00:51:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=202.108.3.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788483092; cv=none; b=THi9R6HcmGeYrl3d0aDf42HznnIBuNWgatr14im9Y7ZIt/x3WF77IZvcyHnfvipCgG1nZSFnAkLAi2+LrzfRfOzXOQZ7kDf6VsCSiCb+6NuvajibsWq+wg4VCJjfr05UdUMKT2b2QabBC2voPdYKNvu3N89OKPdLFXurEQQ23ZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788483092; c=relaxed/simple; bh=bjUTNXGidzIZEyrz+v2s9x6tmUWypnFmcnFdiMziEkU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=M05o5BV/eYPo+Lwn3SVBjFAHGjQIiCf74QuJISd/FD39PnyAQO99m5yFpFVPXjaOfZ6BS4O0EEKt4dnrKNP0JmhhqAE6Z8krSBJ54tx5eYu6YFKaLXo5I3bF+03UPxFyEAqhtZyPNwzriVP+bXxASlOgjBX0zfTZP/sGau3f5tg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com; spf=pass smtp.mailfrom=sina.com; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b=m+GQcQ02; arc=none smtp.client-ip=202.108.3.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b="m+GQcQ02" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1788483088; bh=NHVvGl/JeJlfVlH9Bp7+T+8OJJZfuThp2XTH+28fS0o=; h=From:Subject:Date:Message-ID; b=m+GQcQ02VAv01GDoTUmnQEl6t/McUOP/gopTOELH+IoyZCGMI8mI4pfOu/5tF26PN L6L7Tve9oFBMEAryqqbQ6xtZUyCl3QLm0Tx9aEhZYOayJXe26Zz/khYDMVPoc6b1Xn ISb1ljWeCkwrwEEuAjLobPJpY2xlo347jXITWqxA= X-SMAIL-HELO: localhost.localdomain Received: from unknown (HELO localhost.localdomain)([114.249.62.194]) by sina.com (10.54.253.32) with ESMTP id 6A9A1608000075FD; Fri, 4 Sep 2026 08:51:23 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 4064374456609 X-SMAIL-UIID: A72629F7F0964B8792FFCC7D669E7526-20260904-085123-1 From: Hillf Danton To: Sean Christopherson Cc: syzbot , david@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [kvm?] INFO: task hung in kvm_gmem_release Date: Fri, 4 Sep 2026 08:51:09 +0800 Message-ID: <20260904005111.2069-1-hdanton@sina.com> In-Reply-To: <20260901073343.2002-1-hdanton@sina.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 1 Sep 2026 15:33:42 +0800 Hillf Danton wrote: >On Mon, 31 Aug 2026 08:15:44 -0700 Sean Christopherson wrote: >> >> Marking this invalid, as I'm 99.9% certain guest_memfd is an innocent bystander. >> CPU1 is stuck on an IN instruction (the actual port I/O), and there are a handful >> of identical failures in random subsystems that pop up a few times a month[*]. >> My guess is the host side of the serial port is going out to lunch intermittently. >> >> [*] https://lore.kernel.org/all/?q=%22io_serial_in%22%20syzkaller >> >> #syz invalid >> >The 0.1% uncertainty hints this invalid mark is NOT true or at least earlier >than thought, because a) the IN instruction is not kvm specific [11] and b) the >i2c hang [11] is i2c specific [12]. > >[11] Subject: [syzbot] [i2c?] [usb?] INFO: task hung in em28xx_i2c_unregister >https://lore.kernel.org/lkml/6a95ef74.764875ec.b345.0003.GAE@google.com/ > >[12] Subject: [syzbot] [i2c?] [usb?] INFO: task hung in em28xx_i2c_unregister >https://lore.kernel.org/lkml/6a9676c7.764875ec.b345.0007.GAE@google.com/ > >That said, extra evidence is needed to prove that the serial port is going out >to lunch on the host side. > For archive purpose, the sleeper with nfsd_mutex held [15] explains the nfsd_mutex waiter [16], another case that defies the lunch guess. [15] Subject: [syzbot] [nfs?] INFO: task hung in nfsd4_cld_tracking_init https://lore.kernel.org/lkml/6a99f6f0.2e567484.299ffc.000c.GAE@google.com/ [16] Subject: Re: [syzbot] [nfs?] INFO: task hung in nfsd_nrthreads https://lore.kernel.org/lkml/6a98a3c5.27a413cd.1e878c.0010.GAE@google.com/