Re: [Qemu-devel] [patch v3 7/9] vfio: vote the function 0 to do host bus reset when aer occurred

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

On 03/16/2016 04:38 AM, Alex Williamson wrote:
> On Tue, 15 Mar 2016 09:35:47 +0800
> Cao jin <caoj.fnst@cn.fujitsu.com> wrote:
>
>> From: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
>>
>> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
>> ---
>>   hw/pci/pci.c             |  2 ++
>>   hw/vfio/pci.c            | 14 ++++++++++++++
>>   hw/vfio/pci.h            |  1 +
>>   include/hw/pci/pci_bus.h |  2 ++
>>   4 files changed, 19 insertions(+)
>>
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index e67664d..953745d 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -276,6 +276,8 @@ static void pcibus_reset(BusState *qbus)
>>       for (i = 0; i < bus->nirq; i++) {
>>           assert(bus->irq_count[i] == 0);
>>       }
>> +
>> +    bus->is_bus_rst = false;
>>   }
>>   
>>   static void pci_host_bus_register(DeviceState *host)
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index 223c0ee..b944d0b 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -1901,6 +1901,8 @@ static void vfio_check_hot_bus_reset(VFIOPCIDevice *vdev, Error **errp)
>>       /* List all affected devices by bus reset */
>>       devices = &info->devices[0];
>>   
>> +    vdev->single_depend_dev = (info->count == 1);
>> +
>>       /* Verify that we have all the groups required */
>>       for (i = 0; i < info->count; i++) {
>>           PCIHostDeviceAddress host;
>> @@ -2593,6 +2595,10 @@ static void vfio_err_notifier_handler(void *opaque)
>>           return;
>>       }
>>   
>> +    if ((vdev->features & VFIO_FEATURE_ENABLE_AER)) {
>> +        vdev->pdev.bus->is_bus_rst = true;
>> +    }
>> +
> So we're *assuming* that the next reset will be a bus reset because we
> took an AER fault... what if that particular error got handled in
> another way, maybe a device specific handler that doesn't do a bus
> reset?  The asymmetry of setting a value here and clearing it in PCI
> code is pretty undesirable as well.  Can we detect that the bus is in
> reset on our own given the current set of configuration restrictions?
> Seems pretty easy to test for an AER device with the parent bridge
> having PCI_BRIDGE_CTL_BUS_RESET set and wait for function #0 to do a
> hot reset.  Thanks,
Indeed. Thanks for your help.

Chen
>
> Alex
>
>>       /*
>>        * TBD. Retrieve the error details and decide what action
>>        * needs to be taken. One of the actions could be to pass
>> @@ -3060,6 +3066,14 @@ static void vfio_pci_reset(DeviceState *dev)
>>   
>>       trace_vfio_pci_reset(vdev->vbasedev.name);
>>   
>> +    if (pdev->bus->is_bus_rst) {
>> +        /* simply voting the function 0 to do hot bus reset */
>> +        if (pci_get_function_0(pdev) == pdev) {
>> +            vfio_pci_hot_reset(vdev, vdev->single_depend_dev);
>> +        }
>> +        return;
>> +    }
>> +
>>       vfio_pci_pre_reset(vdev);
>>   
>>       if (vdev->resetfn && !vdev->resetfn(vdev)) {
>> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
>> index aff46c2..32bd31f 100644
>> --- a/hw/vfio/pci.h
>> +++ b/hw/vfio/pci.h
>> @@ -143,6 +143,7 @@ typedef struct VFIOPCIDevice {
>>       bool no_kvm_intx;
>>       bool no_kvm_msi;
>>       bool no_kvm_msix;
>> +    bool single_depend_dev;
>>   } VFIOPCIDevice;
>>   
>>   uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
>> diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
>> index 403fec6..6bcd334 100644
>> --- a/include/hw/pci/pci_bus.h
>> +++ b/include/hw/pci/pci_bus.h
>> @@ -39,6 +39,8 @@ struct PCIBus {
>>          Keep a count of the number of devices with raised IRQs.  */
>>       int nirq;
>>       int *irq_count;
>> +
>> +    bool is_bus_rst;
>>   };
>>   
>>   typedef struct PCIBridgeWindows PCIBridgeWindows;
>
>
> .
>