Re: [PATCH v3 3/9] vfio: add quirk device write method

[Alex Williamson]

On Thu, 16 Jul 2020 18:46:33 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:

> On Tue, 30 Jun 2020 at 13:30, P J P <ppandit@redhat.com> wrote:
> >
> > From: Prasad J Pandit <pjp@fedoraproject.org>
> >
> > Add vfio quirk device mmio write method to avoid NULL pointer
> > dereference issue.
> >
> > Reported-by: Lei Sun <slei.casper@gmail.com>
> > Reviewed-by: Li Qiang <liq3ea@gmail.com>
> > Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> > ---
> >  hw/vfio/pci-quirks.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > Update v3: Add Reviewed-by: ...  
> >   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg09406.html  
> >
> > diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
> > index d304c81148..cc6d5dbc23 100644
> > --- a/hw/vfio/pci-quirks.c
> > +++ b/hw/vfio/pci-quirks.c
> > @@ -14,6 +14,7 @@
> >  #include "config-devices.h"
> >  #include "exec/memop.h"
> >  #include "qemu/units.h"
> > +#include "qemu/log.h"
> >  #include "qemu/error-report.h"
> >  #include "qemu/main-loop.h"
> >  #include "qemu/module.h"
> > @@ -264,8 +265,15 @@ static uint64_t vfio_ati_3c3_quirk_read(void *opaque,
> >      return data;
> >  }
> >
> > +static void vfio_ati_3c3_quirk_write(void *opaque, hwaddr addr,
> > +                                        uint64_t data, unsigned size)
> > +{
> > +    qemu_log_mask(LOG_GUEST_ERROR, "%s not implemented\n", __func__);
> > +}
> > +
> >  static const MemoryRegionOps vfio_ati_3c3_quirk = {
> >      .read = vfio_ati_3c3_quirk_read,
> > +    .write = vfio_ati_3c3_quirk_write,
> >      .endianness = DEVICE_LITTLE_ENDIAN,
> >  };  
> 
> 
> Alex (Williamson) -- as the vfio maintainer, do you have a view
> on whether we should be logging write accesses to port 0x3c3
> here as guest-errors or unimplemented-QEMU-functionality?
> 
> Guest-error seems plausible to me, anyway.

I believe the intention was that writes would be dropped, so if this
generates logging that is going to cause users to file bugs, that would
be undesirable.  Thanks,

Alex