Re: [PATCH] virtio: disable ioeventfd for record/replay

[Pavel Dovgalyuk]

On 11.02.2021 11:44, Cornelia Huck wrote:
> On Thu, 11 Feb 2021 11:34:53 +0300
> Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> wrote:
>
> > virtio devices support separate iothreads waiting for
> > events from file descriptors. These are asynchronous
> > events that can't be recorded and replayed, therefore
> > this patch disables ioeventfd for all devices when
> > record or replay is enabled.
> >
> > Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
> > ---
> >   hw/virtio/virtio-pci.c |    6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 094c36aa3e..76fbc111ea 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -37,6 +37,7 @@
> >   #include "qemu/range.h"
> >   #include "hw/virtio/virtio-bus.h"
> >   #include "qapi/visitor.h"
> > +#include "sysemu/replay.h"
> >   
> >   #define VIRTIO_PCI_REGION_SIZE(dev)     VIRTIO_PCI_CONFIG_OFF(msix_present(dev))
> >   
> > @@ -1746,6 +1747,11 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
> >           proxy->flags &= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD;
> >       }
> >   
> > +    /* fd-based ioevents can't be synchronized in record/replay */
> > +    if (replay_mode != REPLAY_MODE_NONE) {
> > +        proxy->flags &= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD;
> > +    }
> > +
> >       /*
> >        * virtio pci bar layout used by default.
> >        * subclasses can re-arrange things if needed.
>
> I think you would need to do the same for any device using ioeventfd,
> no?

That's right.
It seems, that ioeventfd is used in virtio-ccw, virtio-mmio, and 
virtio-pci. The second one is related to KVM only, right?

And the first one should be updated too for replay.