Re: [PATCH v2 24/30] vfio-pci/zdev: wire up group notifier

[Matthew Rosato <mjrosato@xxxxxxxxxxxxx>]

On 1/18/22 12:34 PM, Pierre Morel wrote:
> On 1/14/22 21:31, Matthew Rosato wrote:
> > KVM zPCI passthrough device logic will need a reference to the associated
> > kvm guest that has access to the device.  Let's register a group notifier
> > for VFIO_GROUP_NOTIFY_SET_KVM to catch this information in order to 
> > create
> > an association between a kvm guest and the host zdev.
> >
> > Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> > ---
> >   arch/s390/include/asm/kvm_pci.h  |  2 ++
> >   drivers/vfio/pci/vfio_pci_core.c |  2 ++
> >   drivers/vfio/pci/vfio_pci_zdev.c | 46 ++++++++++++++++++++++++++++++++
> >   include/linux/vfio_pci_core.h    | 10 +++++++
> >   4 files changed, 60 insertions(+)
> >
> > diff --git a/arch/s390/include/asm/kvm_pci.h 
> > b/arch/s390/include/asm/kvm_pci.h
> > index fa90729a35cf..97a90b37c87d 100644
> > --- a/arch/s390/include/asm/kvm_pci.h
> > +++ b/arch/s390/include/asm/kvm_pci.h
> > @@ -17,6 +17,7 @@
> >   #include <linux/kvm.h>
> >   #include <linux/pci.h>
> >   #include <linux/mutex.h>
> > +#include <linux/notifier.h>
> >   #include <asm/pci_insn.h>
> >   #include <asm/pci_dma.h>
> > @@ -33,6 +34,7 @@ struct kvm_zdev {
> >       u64 rpcit_count;
> >       struct kvm_zdev_ioat ioat;
> >       struct zpci_fib fib;
> > +    struct notifier_block nb;
> >   };
> >   int kvm_s390_pci_dev_open(struct zpci_dev *zdev);
> > diff --git a/drivers/vfio/pci/vfio_pci_core.c 
> > b/drivers/vfio/pci/vfio_pci_core.c
> > index f948e6cd2993..fc57d4d0abbe 100644
> > --- a/drivers/vfio/pci/vfio_pci_core.c
> > +++ b/drivers/vfio/pci/vfio_pci_core.c
> > @@ -452,6 +452,7 @@ void vfio_pci_core_close_device(struct vfio_device 
> > *core_vdev)
> >       vfio_pci_vf_token_user_add(vdev, -1);
> >       vfio_spapr_pci_eeh_release(vdev->pdev);
> > +    vfio_pci_zdev_release(vdev);
> >       vfio_pci_core_disable(vdev);
> >       mutex_lock(&vdev->igate);
> > @@ -470,6 +471,7 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_close_device);
> >   void vfio_pci_core_finish_enable(struct vfio_pci_core_device *vdev)
> >   {
> >       vfio_pci_probe_mmaps(vdev);
> > +    vfio_pci_zdev_open(vdev);
> >       vfio_spapr_pci_eeh_open(vdev->pdev);
> >       vfio_pci_vf_token_user_add(vdev, 1);
> >   }
> > diff --git a/drivers/vfio/pci/vfio_pci_zdev.c 
> > b/drivers/vfio/pci/vfio_pci_zdev.c
> > index ea4c0d2b0663..5c2bddc57b39 100644
> > --- a/drivers/vfio/pci/vfio_pci_zdev.c
> > +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> > @@ -13,6 +13,7 @@
> >   #include <linux/vfio_zdev.h>
> >   #include <asm/pci_clp.h>
> >   #include <asm/pci_io.h>
> > +#include <asm/kvm_pci.h>
> >   #include <linux/vfio_pci_core.h>
> > @@ -136,3 +137,48 @@ int vfio_pci_info_zdev_add_caps(struct 
> > vfio_pci_core_device *vdev,
> >       return ret;
> >   }
> > +
> > +static int vfio_pci_zdev_group_notifier(struct notifier_block *nb,
> > +                    unsigned long action, void *data)
> > +{
> > +    struct kvm_zdev *kzdev = container_of(nb, struct kvm_zdev, nb);
> > +
> > +    if (action == VFIO_GROUP_NOTIFY_SET_KVM) {
> > +        if (!data || !kzdev->zdev)
> > +            return NOTIFY_DONE;
> > +        kvm_s390_pci_attach_kvm(kzdev->zdev, data);
>
> Why not just set kzdev->kvm = data ?
>
> alternatively, define kvm_s390_pci_attach_kvm() as an inline instead of 
> a global function.
>
> otherwise LGTM

At some point in the past this function did more than just set a 
pointer...  You are correct there's no need for this abstraction now, 
let's just set kzdev->kvm = data directly here and drop the 
kvm_s390_pci_attach_kvm function.