From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH] qemu-kvm-x86: consider the irq0override flag in
 kvm_arch_init_irq_routing
Date: Mon, 7 Feb 2011 08:12:59 -0200
Message-ID: <20110207101259.GA20825@amt.cnet>
References: <1284472300-4211-1-git-send-email-bernhard.kohl@nsn.com>
 <4D4FBE7E.8090308@siemens.com>
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Cc: Bernhard Kohl <bernhard.kohl@nsn.com>, kvm@vger.kernel.org
To: Jan Kiszka <jan.kiszka@siemens.com>
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On Mon, Feb 07, 2011 at 10:42:22AM +0100, Jan Kiszka wrote:
> Hi Bernhard,
> 
> On 2010-09-14 15:51, Bernhard Kohl wrote:
> > The setting of the irq0override flag must be also passed properly
> > to the KVM_IRQCHIP_IOAPIC.
> > 
> > Signed-off-by: Bernhard Kohl <bernhard.kohl@nsn.com>
> > ---
> >  qemu-kvm-x86.c |    4 ++--
> >  1 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
> > index fd974b3..e35c234 100644
> > --- a/qemu-kvm-x86.c
> > +++ b/qemu-kvm-x86.c
> > @@ -1388,9 +1388,9 @@ int kvm_arch_init_irq_routing(void)
> >              }
> >          }
> >          for (i = 0; i < 24; ++i) {
> > -            if (i == 0) {
> > +            if (i == 0 && irq0override) {
> >                  r = kvm_add_irq_route(kvm_context, i, KVM_IRQCHIP_IOAPIC, 2);
> > -            } else if (i != 2) {
> > +            } else if (i != 2 || !irq0override) {
> >                  r = kvm_add_irq_route(kvm_context, i, KVM_IRQCHIP_IOAPIC, i);
> >              }
> >              if (r < 0) {
> 
> While cleaning up the irq0override fragments, I stumbled over this
> commit. It is a nop for qemu-kvm, today and also by the time it was applied:
> 
> irq0override = !kvm_irqchip || kvm_has_gsi_routing
> 
> But, for obvious reasons, the code above is only executed when gsi
> routing is available.
> 
> Can you remember what motivated this patch?
> 
> Jan

Guest OS which can't cope with 0->2 GSI->IOAPIC pin mapping.