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

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Message-ID: <20220408124824.GZ64706@ziepe.ca>
Date:   Fri, 8 Apr 2022 09:48:24 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>
Cc:     Matthew Rosato <mjrosato@...ux.ibm.com>,
        linux-s390@...r.kernel.org, alex.williamson@...hat.com,
        cohuck@...hat.com, farman@...ux.ibm.com, pmorel@...ux.ibm.com,
        borntraeger@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        imbrenda@...ux.ibm.com, vneethv@...ux.ibm.com,
        oberpar@...ux.ibm.com, freude@...ux.ibm.com, thuth@...hat.com,
        pasic@...ux.ibm.com, pbonzini@...hat.com, corbet@....net,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 14/21] KVM: s390: pci: provide routines for
 enabling/disabling interrupt forwarding

On Tue, Apr 05, 2022 at 03:39:19PM +0200, 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@...ux.ibm.com>
> >  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
> > +++ 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.

{} is not a GNU extension, it is the preferred way to write it.

The standard has a weird distinction between {} and {0} that results
in different behavior.

Jason