Re: [Qemu-devel] [PATCH v5 5/7] vfio-pci: pass the aer error to guest

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 2015-03-12 at 18:23 +0800, Chen Fan wrote:
> when the vfio device encounters an uncorrectable error in host,
> the vfio_pci driver will signal the eventfd registered by this
> vfio device, the results in the qemu eventfd handler getting
> invoked.
> 
> this patch is to pass the error to guest and have the guest driver
> recover from the error.

What is going to be the typical recovery mechanism for the guest?  I'm
concerned that the topology of the device in the guest doesn't
necessarily match the topology of the device in the host, so if the
guest were to attempt a bus reset to recover a device, for instance,
what happens?

> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 34 ++++++++++++++++++++++++++++------
>  1 file changed, 28 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 0a515b6..8966c49 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -3240,18 +3240,40 @@ static void vfio_put_device(VFIOPCIDevice *vdev)
>  static void vfio_err_notifier_handler(void *opaque)
>  {
>      VFIOPCIDevice *vdev = opaque;
> +    PCIDevice *dev = &vdev->pdev;
> +    PCIEAERMsg msg = {
> +        .severity = 0,
> +        .source_id = (pci_bus_num(dev->bus) << 8) | dev->devfn,
> +    };
>  
>      if (!event_notifier_test_and_clear(&vdev->err_notifier)) {
>          return;
>      }
>  
> +    /* we should read the error details from the real hardware
> +     * configuration spaces, here we only need to do is signaling
> +     * to guest an uncorrectable error has occurred.
> +     */

Inconsistent comment style

> +     if(dev->exp.aer_cap) {
         ^ space

> +        uint8_t *aer_cap = dev->config + dev->exp.aer_cap;
> +        uint32_t uncor_status;
> +        bool isfatal;
> +
> +        uncor_status = vfio_pci_read_config(dev,
> +                           dev->exp.aer_cap + PCI_ERR_UNCOR_STATUS, 4);
> +
> +        isfatal = uncor_status & pci_get_long(aer_cap + PCI_ERR_UNCOR_SEVER);
> +
> +        msg.severity = isfatal ? PCI_ERR_ROOT_CMD_FATAL_EN :
> +                                 PCI_ERR_ROOT_CMD_NONFATAL_EN;
> +
> +        pcie_aer_msg(dev, &msg);
> +        return;
> +    }
> +
>      /*
> -     * TBD. Retrieve the error details and decide what action
> -     * needs to be taken. One of the actions could be to pass
> -     * the error to the guest and have the guest driver recover
> -     * from the error. This requires that PCIe capabilities be
> -     * exposed to the guest. For now, we just terminate the
> -     * guest to contain the error.
> +     * If the aer capability is not exposed to the guest. we just
> +     * terminate the guest to contain the error.
>       */
>  
>      error_report("%s(%04x:%02x:%02x.%x) Unrecoverable error detected.  "