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Re: [Qemu-devel] [PATCH v2] vfio/pci: Support error recovery


From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH v2] vfio/pci: Support error recovery
Date: Tue, 10 Jan 2017 01:04:06 +0200

On Sat, Dec 31, 2016 at 05:15:36PM +0800, Cao jin wrote:
> Support serious device error recovery

serious?

> 
> Signed-off-by: Cao jin <address@hidden>
> ---
>  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.

-- 
MST



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