Re: [PATCH 4/4] s390x/pci: add supported DT information to clp response

[Matthew Rosato]

On 12/3/21 4:33 AM, Pierre Morel wrote:
> On 12/2/21 17:41, Matthew Rosato wrote:
> > The DTSM is a mask that specifies which I/O Address Translation 
> > designation
> > types are supported.  A linux guest today does not look at this field but
>
> Even Linux is the most used guest it is not the only one so may be not 
> mention Linux here.

OK

> > could in the future; let's advertise what QEMU actually supports.
> >
> > Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> > ---
> >   hw/s390x/s390-pci-bus.c         | 1 +
> >   hw/s390x/s390-pci-vfio.c        | 1 +
> >   include/hw/s390x/s390-pci-bus.h | 1 +
> >   include/hw/s390x/s390-pci-clp.h | 3 ++-
> >   4 files changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> > index 1b51a72838..01b58ebc70 100644
> > --- a/hw/s390x/s390-pci-bus.c
> > +++ b/hw/s390x/s390-pci-bus.c
> > @@ -782,6 +782,7 @@ static void s390_pci_init_default_group(void)
> >       resgrp->i = 128;
> >       resgrp->maxstbl = 128;
> >       resgrp->version = 0;
> > +    resgrp->dtsm = ZPCI_DTSM;
>
> OK
>
> >   }
> >   static void set_pbdev_info(S390PCIBusDevice *pbdev)
> > diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
> > index 2a153fa8c9..6f80a47e29 100644
> > --- a/hw/s390x/s390-pci-vfio.c
> > +++ b/hw/s390x/s390-pci-vfio.c
> > @@ -160,6 +160,7 @@ static void s390_pci_read_group(S390PCIBusDevice 
> > *pbdev,
> >           resgrp->i = cap->noi;
> >           resgrp->maxstbl = cap->maxstbl;
> >           resgrp->version = cap->version;
> > +        resgrp->dtsm = ZPCI_DTSM;
>
> Is it safe for VFIO whith interpretation?
> Shouldn't we extend the capability and use the host DTSM in this case?

We will do exactly this when there is an interpretation series.

For the current intercept-based code, QEMU only supports DT 1 for 
passthrough regardless of what the host is supporting and rejects all 
else (see check in reg_ioat)