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Message-ID: <20170110170832-mutt-send-email-mst@kernel.org>
Date: Tue, 10 Jan 2017 17:11:01 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Cao jin <caoj.fnst@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
qemu-devel@...gnu.org, izumi.taku@...fujitsu.com,
alex.williamson@...hat.com
Subject: Re: [PATCH v2] vfio/pci: Support error recovery
On Tue, Jan 10, 2017 at 07:46:17PM +0800, Cao jin wrote:
>
>
> On 01/10/2017 07:04 AM, Michael S. Tsirkin wrote:
> > On Sat, Dec 31, 2016 at 05:15:36PM +0800, Cao jin wrote:
> >> Support serious device error recovery
> >
> > serious?
> >
>
> Sorry for my poor vocabulary if it confuses people. I wanted to express
> the meaning that: vfio-pci actually cannot do a real recovery for device
> even if it provides the callbacks, it relies on the user to do a
> effective(or word "serious"?) recovery.
>
> Welcome the amendment on the commit log.
It's up to Alex, maybe he's able to figure it all out from
code, but the rest of us could benefit from a description
of what the patch does from userspace point of view.
Also, is it a pre-requisite of the userspace patches you posted?
> --
> Sincerely,
> Cao jin
>
> >>
> >> Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
> >> ---
> >> drivers/vfio/pci/vfio_pci.c | 70 +++++++++++++++++++++++++++++++++++--
> >> drivers/vfio/pci/vfio_pci_private.h | 2 ++
> >> 2 files changed, 70 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> >> index 712a849..752af20 100644
> >> --- a/drivers/vfio/pci/vfio_pci.c
> >> +++ b/drivers/vfio/pci/vfio_pci.c
> >> @@ -534,6 +534,15 @@ static long vfio_pci_ioctl(void *device_data,
> >> {
> >> struct vfio_pci_device *vdev = device_data;
> >> unsigned long minsz;
> >> + int ret;
> >> +
> >> + if (vdev->aer_recovering && (cmd == VFIO_DEVICE_SET_IRQS ||
> >> + cmd == VFIO_DEVICE_RESET || cmd == VFIO_DEVICE_PCI_HOT_RESET)) {
> >> + ret = wait_for_completion_interruptible(
> >> + &vdev->aer_completion);
> >
> > don't split it like that.
> >
> >> + if (ret)
> >> + return ret;
> >> + }
> >>
> >> if (cmd == VFIO_DEVICE_GET_INFO) {
> >> struct vfio_device_info info;
> >> @@ -953,6 +962,15 @@ static ssize_t vfio_pci_rw(void *device_data, char __user *buf,
> >> {
> >> unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> >> struct vfio_pci_device *vdev = device_data;
> >> + int ret;
> >> +
> >> + /* block all kinds of access during host recovery */
> >> + if (vdev->aer_recovering) {
> >> + ret = wait_for_completion_interruptible(
> >> + &vdev->aer_completion);
> >> + if (ret)
> >> + return ret;
> >> + }
> >>
> >> if (index >= VFIO_PCI_NUM_REGIONS + vdev->num_regions)
> >> return -EINVAL;
> >> @@ -1117,6 +1135,7 @@ 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_completion);
> >>
> >> ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
> >> if (ret) {
> >> @@ -1176,6 +1195,9 @@ 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;
> >> + unsigned int aer_cap_offset;
> >> + int ret;
> >>
> >> device = vfio_device_get_from_dev(&pdev->dev);
> >> if (device == NULL)
> >> @@ -1187,10 +1209,29 @@ 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,
> >
> > should be "Get".
> >
> >> + * 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_info("device %d got AER detect notification. uncorrectable error status = 0x%x\n", pdev->devfn, uncor_status);//to be removed
> >
> > Pls drop this.
> >
> >> mutex_lock(&vdev->igate);
> >>
> >> - if (vdev->err_trigger)
> >> - eventfd_signal(vdev->err_trigger, 1);
> >> + vdev->aer_recovering = true;
> >> + reinit_completion(&vdev->aer_completion);
> >> +
> >> + if (vdev->err_trigger && uncor_status) {
> >> + pr_info("device %d signal uncor status 0x%x to user",
> >> + pdev->devfn, uncor_status);
> >> + /* signal uncorrectable error status to user space */
> >> + eventfd_signal(vdev->err_trigger, uncor_status);
> >> + }
> >>
> >> mutex_unlock(&vdev->igate);
> >>
> >> @@ -1199,8 +1240,33 @@ 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;
> >> + }
> >> +
> >> + mutex_lock(&vdev->igate);
> >> + vdev->aer_recovering = false;
> >> + mutex_unlock(&vdev->igate);
> >> +
> >> + complete_all(&vdev->aer_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..ba8471f 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_completion;
> >> struct pci_saved_state *pci_saved_state;
> >> int refcnt;
> >> struct eventfd_ctx *err_trigger;
> >> --
> >> 1.8.3.1
> >>
> >>
> >
> > How about some explanation about what is going on here? All these
> > changes seem racy since any number of errors can trigger at any time.
> >
>
>
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