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

[Chen Fan]

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 <address@hidden>
> > ---
> >   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.  "
>
>
> .