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

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Date:   Tue, 5 Apr 2022 17:06:23 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        farman@...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 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@...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
>>> --- 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