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From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Julia Suvorova <jusual@redhat.com>,
	"open list:VFIO DRIVER" <kvm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] KVM: x86: Use MMCONFIG for all PCI config space accesses
Date: Fri, 31 Jul 2020 12:41:06 +0300
Message-ID: <CAHp75Vfp8aabZo_NW78kM-OLLKDgK1CwvLZNwmPZyQgaw6bXtQ@mail.gmail.com> (raw)
In-Reply-To: <873658kpj2.fsf@vitty.brq.redhat.com>

On Fri, Jul 31, 2020 at 12:22 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> Andy Shevchenko <andy.shevchenko@gmail.com> writes:
> > On Thu, Jul 30, 2020 at 10:37 PM Julia Suvorova <jusual@redhat.com> wrote:

...

> >> +static int __init kvm_pci_arch_init(void)
> >> +{
> >> +       if (raw_pci_ext_ops &&

> >> +               return 0;
> >> +       }
> >
> >> +       return 1;
> >
> > Hmm... I don't remember what positive codes means there. Perhaps you
> > need to return a rather error code?
>
> If I'm reading the code correctly,
>
> pci_arch_init() has the following:
>
>         if (x86_init.pci.arch_init && !x86_init.pci.arch_init())
>                 return 0;
>
>
> so returning '1' here means 'continue' and this seems to be
> correct. (E.g. Hyper-V's hv_pci_init() does the same). What I'm not sure
> about is 'return 0' above as this will result in skipping the rest of
> pci_arch_init(). Was this desired or should we return '1' in both cases?

I think it depends what you want. In complex cases we recognize three
possibilities

-ERRNO: function failed, we have to stop and bailout with error from callee
0: function OK, stop and return 0
1: function OK, continue the rest in callee

Do we have needs in this or is the current enough for all (exist) callees?

-- 
With Best Regards,
Andy Shevchenko

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 19:35 Julia Suvorova
2020-07-30 19:50 ` Andy Shevchenko
2020-07-31  9:22   ` Vitaly Kuznetsov
2020-07-31  9:41     ` Andy Shevchenko [this message]
2020-07-31 18:23     ` Julia Suvorova

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