Re: [Qemu-devel] [qemu-s390x] [PATCH for-4.1 1/2] s390x/pci: add some fallthrough annotations

[Collin Walling]

On 7/17/19 5:27 AM, Christian Borntraeger wrote:
> On 17.07.19 10:54, Cornelia Huck wrote:
> > On Tue, 16 Jul 2019 14:34:22 -0400
> > Collin Walling <address@hidden> wrote:
> >
> > > On 7/16/19 11:20 AM, Cornelia Huck wrote:
> > > > On Wed, 10 Jul 2019 10:20:41 +0200
> > > > Cornelia Huck <address@hidden> wrote:
> > > >    
> > > > > On Tue, 9 Jul 2019 18:55:34 -0400
> > > > > Collin Walling <address@hidden> wrote:
> > > > >   
> > > > > > On 7/8/19 9:23 AM, Christian Borntraeger wrote:
> > > > > > > On 08.07.19 14:54, Cornelia Huck wrote:
> > > > > > > > According to the comment, the bits are supposed to accumulate.
> > > > > > > >
> > > > > > > > Reported-by: Stefan Weil <address@hidden>
> > > > > > > > Fixes: 5d1abf234462 ("s390x/pci: enforce zPCI state checking")
> > > > > > > > Signed-off-by: Cornelia Huck <address@hidden>
> > > > > > >
> > > > > > > This patch does not change behaviour, so it is certainly not wrong.
> > > > > > >
> > > > > > > So lets have a look at if the bug report was actually a real bug or
> > > > > > > just a missing annotation.
> > > > > > >         
> > > > > > > > ---
> > > > > > > >     hw/s390x/s390-pci-inst.c | 2 ++
> > > > > > > >     1 file changed, 2 insertions(+)
> > > > > > > >
> > > > > > > > diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
> > > > > > > > index 61f30b8e55d2..00235148bed7 100644
> > > > > > > > --- a/hw/s390x/s390-pci-inst.c
> > > > > > > > +++ b/hw/s390x/s390-pci-inst.c
> > > > > > > > @@ -1209,8 +1209,10 @@ int stpcifc_service_call(S390CPU *cpu, uint8_t r1, 
> > > > > > > > uint64_t fiba, uint8_t ar,
> > > > > > > >          * FH Enabled bit is set to one in states of ENABLED, BLOCKED or ERROR. 
> > > > > > > > */
> > > > > > > >         case ZPCI_FS_ERROR:
> > > > > > > >             fib.fc |= 0x20;
> > > > > > > > +        /* fallthrough */
> > > > > > >
> > > > > > > This is correct, in case of an error we are also blocked.
> > > > > > >         
> > > > > >
> > > > > > Agreed. This is definitely correct based on our architecture.
> > > > > >       
> > > > > > > >         case ZPCI_FS_BLOCKED:
> > > > > > > >             fib.fc |= 0x40;
> > > > > > > > +        /* fallthrough */
> > > > > > >
> > > > > > > I think this is also correct, but  it would be good if Collin could verify.
> > > > > > >         
> > > > > >
> > > > > > I failed to find anything to support setting the function control
> > > > > > enabled bit when the function state is in error / blocked. I'm
> > > > > > assuming this might be some QEMU hack to get things working? I'll have
> > > > > > to dive further to understand why this was done this way, as it doesn't
> > > > > > align with how the s390x architecture is documented. It's confusing.
> > > > >
> > > > > Might this also be a real issue? Not matching the architecture is not a
> > > > > good sign...
> > > >
> > > > Friendly ping. If we still want to have this patch or a fix in 4.1, we
> > > > need to find out soon...
> > > >    
> > >
> > > Let's take it for now.
> > >
> > > Acked-by: Collin Walling <address@hidden>
> >
> > Just to be clear: You think that the current code is correct AFAYCS?
>   
> I also looked into this again.
> There is a possibility to also be in disabled state.
>  From what I can see, it makes sense that blocked and error belong to the 
> enable state
> so the patch seems correct.

Yes I agree. The material I referenced required me to look over a few
times and ask around a bit. The patch is good. Apologies for my
ambiguous response.