From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753222AbdEESd3 (ORCPT ); Fri, 5 May 2017 14:33:29 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58442 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751716AbdEESdZ (ORCPT ); Fri, 5 May 2017 14:33:25 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefano Stabellini , Juergen Gross , Julia Lawall Subject: [PATCH 3.18 08/68] xen/x86: dont lose event interrupts Date: Fri, 5 May 2017 11:31:53 -0700 Message-Id: <20170505183212.927463181@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170505183212.587141964@linuxfoundation.org> References: <20170505183212.587141964@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stefano Stabellini commit c06b6d70feb32d28f04ba37aa3df17973fd37b6b upstream. On slow platforms with unreliable TSC, such as QEMU emulated machines, it is possible for the kernel to request the next event in the past. In that case, in the current implementation of xen_vcpuop_clockevent, we simply return -ETIME. To be precise the Xen returns -ETIME and we pass it on. However the result of this is a missed event, which simply causes the kernel to hang. Instead it is better to always ask the hypervisor for a timer event, even if the timeout is in the past. That way there are no lost interrupts and the kernel survives. To do that, remove the VCPU_SSHOTTMR_future flag. Signed-off-by: Stefano Stabellini Acked-by: Juergen Gross Cc: Julia Lawall Signed-off-by: Greg Kroah-Hartman --- arch/x86/xen/time.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -362,11 +362,11 @@ static int xen_vcpuop_set_next_event(uns WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT); single.timeout_abs_ns = get_abs_timeout(delta); - single.flags = VCPU_SSHOTTMR_future; + /* Get an event anyway, even if the timeout is already expired */ + single.flags = 0; ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single); - - BUG_ON(ret != 0 && ret != -ETIME); + BUG_ON(ret != 0); return ret; }