From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42777) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGu1U-0004dL-5S for qemu-devel@nongnu.org; Wed, 06 Jan 2016 14:45:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aGu1T-00083i-49 for qemu-devel@nongnu.org; Wed, 06 Jan 2016 14:45:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42062) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aGu1S-00083R-Ve for qemu-devel@nongnu.org; Wed, 06 Jan 2016 14:45:31 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 96853ABBAD for ; Wed, 6 Jan 2016 19:45:30 +0000 (UTC) From: Laurent Vivier Date: Wed, 6 Jan 2016 20:45:25 +0100 Message-Id: <1452109525-32150-3-git-send-email-lvivier@redhat.com> In-Reply-To: <1452109525-32150-1-git-send-email-lvivier@redhat.com> References: <1452109525-32150-1-git-send-email-lvivier@redhat.com> Subject: [Qemu-devel] [PATCH v2 2/2] ohci: clear pending SOF on suspend List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: lvivier@redhat.com, thuth@redhat.com, kraxel@redhat.com On overcommitted CPU, kernel can be so slow that an interrupt can be triggered by the device whereas the driver is not ready to receive it. This drives us into an infinite loop. On suspend, if a SOF interrupt is raised between the stop of the device processing and the change of the device internal state to OHCI_USB_SUSPEND (QEMU stops SOF timer on this state change), this interrupt is never acknowledged. This patch clears pending SOF interrupt on OHCI_USB_SUSPEND setting. Some details: - ohci_irq(): the OHCI interrupt handler, acknowledges the SOF IRQ only if the state of the driver (rh_state) is OHCI_STATE_RUNNING. So if this interrupt happens and the driver is not in this state, the function is called again and again, moving the system to a CPU starvation. - ohci_rh_suspend(): the function stop the operation and acknowledge pending interrupts (but doesn't disable it). Later in the function, the device is moved to OHCI_SUSPEND_STATE, and the driver to OHCI_RH_SUSPENDED. If between the moment when the interrupt is acknowledged and the moment when the device is suspended a new interrupt is raised, it will be never acknowledged because the driver is now not in OHCI_RH_RUNNING state. Signed-off-by: Laurent Vivier --- hw/usb/hcd-ohci.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c index a44fab2..b99e44f 100644 --- a/hw/usb/hcd-ohci.c +++ b/hw/usb/hcd-ohci.c @@ -1446,6 +1446,9 @@ static void ohci_set_ctl(OHCIState *ohci, uint32_t val) break; case OHCI_USB_SUSPEND: ohci_bus_stop(ohci); + /* clear pending SF otherwise linux driver loops in ohci_irq() */ + ohci->intr_status &= ~OHCI_INTR_SF; + ohci_intr_update(ohci); break; case OHCI_USB_RESUME: trace_usb_ohci_resume(ohci->name); -- 1.8.3.1