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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 EF5E6C2D0E4 for ; Mon, 23 Nov 2020 12:58:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A19EC206D9 for ; Mon, 23 Nov 2020 12:58:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XWupPCjM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387879AbgKWM55 (ORCPT ); Mon, 23 Nov 2020 07:57:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:35846 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387634AbgKWMvj (ORCPT ); Mon, 23 Nov 2020 07:51:39 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E3122100A; Mon, 23 Nov 2020 12:51:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1606135897; bh=gefadVBfiGeyhr6C+XK6HN1P6O1jPeS/pEyIBC7j8i0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XWupPCjMttgtrFAkXiOx9alE9OGkgEnB61oMiX08TvrH6hsKO4d5Kuglz/QJ5q4t/ sSt8SRkY+rXOk/6tkKQ6UnZcSvAqGkSJ27Y/N1dxGaIDwYxic5vewinF/q88phx0xI mlCKvvZzZ66QNzXDhVua83tWyZLOfTa+dgqi5b1I= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chris Co , "Andrea Parri (Microsoft)" , Wei Liu Subject: [PATCH 5.9 235/252] Drivers: hv: vmbus: Allow cleanup of VMBUS_CONNECT_CPU if disconnected Date: Mon, 23 Nov 2020 13:23:05 +0100 Message-Id: <20201123121846.919000503@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201123121835.580259631@linuxfoundation.org> References: <20201123121835.580259631@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chris Co commit 92e4dc8b05663d6539b1b8375f3b1cf7b204cfe9 upstream. When invoking kexec() on a Linux guest running on a Hyper-V host, the kernel panics. RIP: 0010:cpuhp_issue_call+0x137/0x140 Call Trace: __cpuhp_remove_state_cpuslocked+0x99/0x100 __cpuhp_remove_state+0x1c/0x30 hv_kexec_handler+0x23/0x30 [hv_vmbus] hv_machine_shutdown+0x1e/0x30 machine_shutdown+0x10/0x20 kernel_kexec+0x6d/0x96 __do_sys_reboot+0x1ef/0x230 __x64_sys_reboot+0x1d/0x20 do_syscall_64+0x6b/0x3d8 entry_SYSCALL_64_after_hwframe+0x44/0xa9 This was due to hv_synic_cleanup() callback returning -EBUSY to cpuhp_issue_call() when tearing down the VMBUS_CONNECT_CPU, even if the vmbus_connection.conn_state = DISCONNECTED. hv_synic_cleanup() should succeed in the case where vmbus_connection.conn_state is DISCONNECTED. Fix is to add an extra condition to test for vmbus_connection.conn_state == CONNECTED on the VMBUS_CONNECT_CPU and only return early if true. This way the kexec() path can still shut everything down while preserving the initial behavior of preventing CPU offlining on the VMBUS_CONNECT_CPU while the VM is running. Fixes: 8a857c55420f29 ("Drivers: hv: vmbus: Always handle the VMBus messages on CPU0") Signed-off-by: Chris Co Reviewed-by: Andrea Parri (Microsoft) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20201110190118.15596-1-chrco@linux.microsoft.com Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman --- drivers/hv/hv.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/drivers/hv/hv.c +++ b/drivers/hv/hv.c @@ -244,9 +244,13 @@ int hv_synic_cleanup(unsigned int cpu) /* * Hyper-V does not provide a way to change the connect CPU once - * it is set; we must prevent the connect CPU from going offline. + * it is set; we must prevent the connect CPU from going offline + * while the VM is running normally. But in the panic or kexec() + * path where the vmbus is already disconnected, the CPU must be + * allowed to shut down. */ - if (cpu == VMBUS_CONNECT_CPU) + if (cpu == VMBUS_CONNECT_CPU && + vmbus_connection.conn_state == CONNECTED) return -EBUSY; /*