Re: [Qemu-devel] [PATCH] hw/pci/pci-stub: Add msi_enabled() and msi_notify() to the pci stubs

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Feb 19, 2019 at 07:24:40PM +0100, Paolo Bonzini wrote:
> On 19/02/19 17:07, Thomas Huth wrote:
> > Some machines have an AHCI adapter, but no PCI. To be able to
> > compile hw/ide/ahci.c without CONFIG_PCI, we still need the two
> > functions msi_enabled() and msi_notify() for linking.
> > This is required for the upcoming Kconfig-like build system, if
> > a user wants to compile a QEMU binary with just one machine that
> > has AHCI, but no PCI, like the ARM "cubieboard" for example.
> > 
> > Signed-off-by: Thomas Huth <thuth@redhat.com>
> > ---
> >  hw/pci/pci-stub.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/hw/pci/pci-stub.c b/hw/pci/pci-stub.c
> > index b941a0e..c04a5df 100644
> > --- a/hw/pci/pci-stub.c
> > +++ b/hw/pci/pci-stub.c
> > @@ -53,3 +53,14 @@ uint16_t pci_requester_id(PCIDevice *dev)
> >      g_assert(false);
> >      return 0;
> >  }
> > +
> > +/* Required by ahci.c */
> > +bool msi_enabled(const PCIDevice *dev)
> > +{
> > +    return false;
> > +}
> > +
> > +void msi_notify(PCIDevice *dev, unsigned int vector)
> > +{
> > +    g_assert_not_reached();
> > +}
> > 
> 
> Makes sense, but it is also abstraction time. :)  What if instead there
> was a function
> 
> void msi_allocate_irqs(PCIDevice *pdev, int num, bool fallback_to_intx);
> 
> and then ich.c did
> 
>     irqs = msi_allocate_irqs(pdev, 1, true);
>     s->irq = irqs[0];
>     g_free(irqs);
> 
> ?  "if msi_enabled raise MSI else raise INTX" is really a common idiom.
> 
> Thanks,
> 
> Paolo

Maybe it is but the specific issue is not about fallback to INTX of PCI
(is the fallback broken for ahci? I don't know).
The trick is there's no pdev at all.

-- 
MST