Re: [PATCH v5 14/21] KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding

[Pierre Morel]

On 4/5/22 15:48, Matthew Rosato wrote:
> On 4/5/22 9:39 AM, Niklas Schnelle wrote:
> > On Mon, 2022-04-04 at 13:43 -0400, Matthew Rosato wrote:
> > > These routines will be wired into a kvm ioctl in order to respond to
> > > requests to enable / disable a device for Adapter Event Notifications /
> > > Adapter Interuption Forwarding.
> > >
> > > Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> > > ---
> > >   arch/s390/kvm/pci.c      | 247 +++++++++++++++++++++++++++++++++++++++
> > >   arch/s390/kvm/pci.h      |   1 +
> > >   arch/s390/pci/pci_insn.c |   1 +
> > >   3 files changed, 249 insertions(+)
> > >
> > > diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
> > > index 01bd8a2f503b..f0fd68569a9d 100644
> > > --- a/arch/s390/kvm/pci.c
> > > +++ b/arch/s390/kvm/pci.c
> > > @@ -11,6 +11,7 @@
> > >   #include <linux/pci.h>
> > >   #include <asm/pci.h>
> > >   #include <asm/pci_insn.h>
> > > +#include <asm/pci_io.h>
> > >   #include "pci.h"
> > >   struct zpci_aift *aift;
> > > @@ -152,6 +153,252 @@ int kvm_s390_pci_aen_init(u8 nisc)
> > >       return rc;
> > >   }
> > > +/* Modify PCI: Register floating adapter interruption forwarding */
> > > +static int kvm_zpci_set_airq(struct zpci_dev *zdev)
> > > +{
> > > +    u64 req = ZPCI_CREATE_REQ(zdev->fh, 0, ZPCI_MOD_FC_REG_INT);
> > > +    struct zpci_fib fib = {};
> >
> > Hmm this one uses '{}' as initializer while all current callers of
> > zpci_mod_fc() use '{0}'. As far as I know the empty braces are a GNU
> > extension so should work for the kernel but for consistency I'd go with
> > '{0}' or possibly '{.foo = bar, ...}' where that is more readable.
> > There too uninitialized fields will be set to 0. Unless of course there
> > is a conflicting KVM convention that I don't know about.
>
> No convention that I'm aware of, I previously had fib = {0} based on the 
> same rationale you describe and changed to fib = {} per review request 
> from Pierre a few versions back.  I don't have a strong preference, but 
> I did not note any functional difference between the two and see a bunch 
> of examples of both methods throughout the kernel.

Was stupid of me to comment that, as you said there are no difference, 
so do as you want.


--
Pierre Morel
IBM Lab Boeblingen