From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754244AbcK1DAK (ORCPT ); Sun, 27 Nov 2016 22:00:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50230 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753929AbcK1DAG (ORCPT ); Sun, 27 Nov 2016 22:00:06 -0500 Date: Mon, 28 Nov 2016 05:00:04 +0200 From: "Michael S. Tsirkin" To: Cao jin Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, izumi.taku@jp.fujitsu.com, alex.williamson@redhat.com Subject: Re: [PATCH] vfio/pci: Support error recovery Message-ID: <20161128045506-mutt-send-email-mst@kernel.org> References: <1480246457-10368-1-git-send-email-caoj.fnst@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1480246457-10368-1-git-send-email-caoj.fnst@cn.fujitsu.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 28 Nov 2016 03:00:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 27, 2016 at 07:34:17PM +0800, Cao jin wrote: > It is user space driver's or device-specific driver's(in guest) responsbility > to do a serious recovery when error happened. Link-reset is one part of > recovery, when pci device is assigned to VM via vfio, link-reset will do > twice in host & guest separately, which will cause many trouble for a > successful recovery, so, disable the vfio-pci's link-reset in aer driver > in host, this is a keypoint for guest to do error recovery successfully. > > CC: alex.williamson@redhat.com > CC: mst@redhat.com > Signed-off-by: Cao jin > --- > This is actually a RFC version(has debug lines left), and has minor changes in > aer driver, so I think maybe it is better not to CC pci guys in this round. > Later will do. > > drivers/pci/pcie/aer/aerdrv_core.c | 12 ++++++- > drivers/vfio/pci/vfio_pci.c | 63 +++++++++++++++++++++++++++++++++++-- > drivers/vfio/pci/vfio_pci_private.h | 2 ++ > 3 files changed, 74 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c > index 521e39c..289fb8e 100644 > --- a/drivers/pci/pcie/aer/aerdrv_core.c > +++ b/drivers/pci/pcie/aer/aerdrv_core.c > @@ -496,7 +496,17 @@ static void do_recovery(struct pci_dev *dev, int severity) > "error_detected", > report_error_detected); > > - if (severity == AER_FATAL) { > + /* vfio-pci as a general meta driver, it actually couldn't do any real > + * recovery for device. It is user space driver, or device-specific > + * driver in guest who should take care of the serious error recovery, > + * link reset actually is one part of whole recovery. Doing reset_link > + * in aer driver of host kernel for vfio-pci devices will cause many > + * trouble for user space driver or guest's device-specific driver, > + * for example: the serious recovery often need to read register in > + * config space, but if register reading happens during link-resetting, > + * it is quite possible to return invalid value like all F's, which > + * will result in unpredictable error. */ Fix multi-comment style please. > + if (severity == AER_FATAL && strcmp(dev->driver->name, "vfio-pci")) { You really want some flag in the device, or something similar. Also, how do we know driver is not going away at this point? > result = reset_link(dev); > if (result != PCI_ERS_RESULT_RECOVERED) > goto failed; > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c > index 712a849..aefd751 100644 > --- a/drivers/vfio/pci/vfio_pci.c > +++ b/drivers/vfio/pci/vfio_pci.c > @@ -535,6 +535,15 @@ static long vfio_pci_ioctl(void *device_data, > struct vfio_pci_device *vdev = device_data; > unsigned long minsz; > > + if (vdev->aer_recovering && (cmd == VFIO_DEVICE_SET_IRQS || > + cmd == VFIO_DEVICE_RESET || cmd == VFIO_DEVICE_PCI_HOT_RESET)) { > + int ret; > + ret = wait_for_completion_interruptible( > + &vdev->aer_error_completion); > + if (ret) > + return ret; > + } > + > if (cmd == VFIO_DEVICE_GET_INFO) { > struct vfio_device_info info; > > @@ -1117,6 +1126,7 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id) > vdev->irq_type = VFIO_PCI_NUM_IRQS; > mutex_init(&vdev->igate); > spin_lock_init(&vdev->irqlock); > + init_completion(&vdev->aer_error_completion); > > ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev); > if (ret) { > @@ -1176,6 +1186,9 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev, > { > struct vfio_pci_device *vdev; > struct vfio_device *device; > + u32 uncor_status = 0; > + unsigned int aer_cap_offset = 0; > + int ret; > > device = vfio_device_get_from_dev(&pdev->dev); > if (device == NULL) > @@ -1187,10 +1200,30 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev, > return PCI_ERS_RESULT_DISCONNECT; > } > > + /* get device's uncorrectable error status as soon as possible, > + * and signal it to user space. The later we read it, the possibility > + * the register value is mangled grows. */ > + aer_cap_offset = pci_find_ext_capability(vdev->pdev, PCI_EXT_CAP_ID_ERR); > + ret = pci_read_config_dword(vdev->pdev, aer_cap_offset + > + PCI_ERR_UNCOR_STATUS, &uncor_status); > + if (ret) > + return PCI_ERS_RESULT_DISCONNECT; > + > + pr_err("device %d got AER detect notification. uncorrectable error status = 0x%x\n", pdev->devfn, uncor_status);//to be removed > mutex_lock(&vdev->igate); > + > + vdev->aer_recovering = true; > + reinit_completion(&vdev->aer_error_completion); > + > + /* suspend config space access from user space, > + * when vfio-pci's error recovery process is on */ what about access to memory etc? Do you need to suspend this as well? > + pci_cfg_access_trylock(vdev->pdev); If you trylock, you need to handle failure. > > - if (vdev->err_trigger) > - eventfd_signal(vdev->err_trigger, 1); > + if (vdev->err_trigger && uncor_status) { > + pr_err("device %d signal uncor status to user space", pdev->devfn);//may be removed > + /* signal uncorrectable error status to user space */ > + eventfd_signal(vdev->err_trigger, uncor_status); > + } > > mutex_unlock(&vdev->igate); > > @@ -1199,8 +1232,34 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev, > return PCI_ERS_RESULT_CAN_RECOVER; > } > > +static void vfio_pci_aer_resume(struct pci_dev *pdev) > +{ > + struct vfio_pci_device *vdev; > + struct vfio_device *device; > + > + device = vfio_device_get_from_dev(&pdev->dev); > + if (device == NULL) > + return; > + > + vdev = vfio_device_data(device); > + if (vdev == NULL) { > + vfio_device_put(device); > + return; > + } > + > + /* vfio-pci's error recovery is done, time to > + * resume pci config space's accesses */ > + pci_cfg_access_unlock(vdev->pdev); pci_cfg_access blocks accesses through sysfs. I would not bother, focus on accesses through vfio. > + > + vdev->aer_recovering = false; don't you need locks when changing aer_recovering? > + complete_all(&vdev->aer_error_completion); > + > + vfio_device_put(device); > +} > + > static const struct pci_error_handlers vfio_err_handlers = { > .error_detected = vfio_pci_aer_err_detected, > + .resume = vfio_pci_aer_resume, > }; > > static struct pci_driver vfio_pci_driver = { > diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h > index 8a7d546..ebf1041 100644 > --- a/drivers/vfio/pci/vfio_pci_private.h > +++ b/drivers/vfio/pci/vfio_pci_private.h > @@ -83,6 +83,8 @@ struct vfio_pci_device { > bool bardirty; > bool has_vga; > bool needs_reset; > + bool aer_recovering; > + struct completion aer_error_completion; > struct pci_saved_state *pci_saved_state; > int refcnt; > struct eventfd_ctx *err_trigger; > -- > 1.8.3.1 > >