Re: [Qemu-devel] [PATCH] pci: Don't deliver MSI/MSI-X messages if bus master support is off

[Paolo Bonzini <pbonzini@redhat.com>]

Il 20/07/2014 21:48, Michael S. Tsirkin ha scritto:
> I guess an alternative is for callers to check before
> invoking msi_notify. Please note is this is only option
> when using e.g. irqfd, so this has some advantages.
> Is there a specific device that is affected by this?
> I would expect drivers to disable msi before clearing
> bus master bit ...
> 
>> > ---
>> >  hw/pci/msi.c  | 4 ++++
>> >  hw/pci/msix.c | 4 ++++
>> >  2 files changed, 8 insertions(+)
>> > 
>> > diff --git a/hw/pci/msi.c b/hw/pci/msi.c
>> > index a4a3040..36b651b 100644
>> > --- a/hw/pci/msi.c
>> > +++ b/hw/pci/msi.c
>> > @@ -285,6 +285,10 @@ void msi_notify(PCIDevice *dev, unsigned int vector)
>> >          return;
>> >      }
>> >  
>> > +    if (!(pci_get_word(dev->config + PCI_COMMAND) & PCI_COMMAND_MASTER)) {
>> > +        return;
>> > +    }
>> > +
>> >      msg = msi_get_message(dev, vector);
>> >  
>> >      MSI_DEV_PRINTF(dev,
>> > diff --git a/hw/pci/msix.c b/hw/pci/msix.c
>> > index 5c49bfc..c77ae7d 100644
>> > --- a/hw/pci/msix.c
>> > +++ b/hw/pci/msix.c
>> > @@ -437,6 +437,10 @@ void msix_notify(PCIDevice *dev, unsigned vector)
>> >          return;
>> >      }
>> >  
>> > +    if (!(pci_get_word(dev->config + PCI_COMMAND) & PCI_COMMAND_MASTER)) {
>> > +        return;
>> > +    }
>> > +
>> >      msg = msix_get_message(dev, vector);
>> >  
>> >      stl_le_phys(&address_space_memory, msg.address, msg.data);


I think a better way to do this, is to use the PCI bus master address
space instead of address_space_memory.

Even if it doesn't fix irqfd, it will make the MSI write go through the
IOMMU as it should.

Paolo