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

[Chen Fan <chen.fan.fnst@cn.fujitsu.com>]

On 03/14/2015 06:34 AM, Alex Williamson wrote:
> 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?
the recovery mechanism is that when guest got an aer error from a device,
guest will clean the corresponding status bit in device register. and for
need reset device, the guest aer driver would reset all devices under bus.

Thanks,
Chen


>> 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.  "
>
>
> .
>