Re: [Qemu-devel] [patch v5 11/12] vfio: device may stuck in D3 when doing aer recovery

[Chen Fan]

On 03/25/2016 06:54 AM, Alex Williamson wrote:
> On Wed, 23 Mar 2016 18:12:06 +0800
> Cao jin <address@hidden> wrote:
>
> > From: Chen Fan <address@hidden>
> >
> > when a physical device aer occurred, the device state probably
> > is not in D0 in a short time, if we recover the device quickly.
> > we may stuck in D3 state when force to change device state to D0.
> > we may need to wait for a short time to inject the error to guest.
> >
> > Signed-off-by: Chen Fan <address@hidden>
> > ---
> >   hw/vfio/pci.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> > index 25fc095..5216e7f 100644
> > --- a/hw/vfio/pci.c
> > +++ b/hw/vfio/pci.c
> > @@ -2658,6 +2658,9 @@ static void vfio_err_notifier_handler(void *opaque)
> >           msg.severity = isfatal ? PCI_ERR_ROOT_CMD_FATAL_EN :
> >                                    PCI_ERR_ROOT_CMD_NONFATAL_EN;
> >   
> > +        /* wait a bit to ensure aer device is ready */
> > +        usleep(2 * 1000);
> Where does this number come from?  Why would the device be in D3?  I
> don't understand this at all.
Hi Alex,

    when I tested the code in my environment, I found that when I used
the aer-inject module to inject a fake aer error to device on host, the qemu
would throw out the message "vfio: Unable to power on device, stuck in D3"
on and off. if I use "gdb" to debug the vfio_pci_pre_reset, the phenomenon
would not appearance, I just thought it should be some timing race issue,
so I use a sleep() to wait 2ms (double the reset time of 1ms) to ensure the
device state is ready. maybe the root reason still need to be 
investigated deeply.

Thanks,
Chen


> > +
> >           pcie_aer_msg(dev, &msg);
> >           return;
> >       }
>
>
> .