On Tue, Nov 22, 2016 at 04:08:50PM +0800, Peter Xu wrote:
> We are very strict in the past getting MSIs from commit
> d1f6af6a1 ("kvm-irqchip: simplify kvm_irqchip_add_msi_route"), assuming
> that MSI should be configured before hand when fetching. When we have
> unrecognized configurations, we panic the system. However looks like
> this is too strict to be working on some platform, and issues occured.
> Firstly it's found on a ppc case and fixed by David in:
>
> 6d17a01 vfio/pci: Fix regression in MSI routing configuration
>
> However we encountered another case now with windows virtio driver and
> reported (and possibly more):
>
> http://bugs.debian.org/844361
>
> To make every driver/hardware happy, let's loosen the rule and go back
> to the original behavior - instead of panic the system, when we try to
> fetch MSI without configured MSI/MSI-X system, we just provide an empty
> message to make drivers happy.
>
> Reported-by: Maciej Kotliński <makotlin...@gmail.com>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> hw/pci/pci.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 24fae16..0cd2bb0 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -2606,9 +2606,11 @@ MSIMessage pci_get_msi_message(PCIDevice *dev, int
> vector)
> } else if (msi_enabled(dev)) {
> msg = msi_get_message(dev, vector);
> } else {
> - /* Should never happen */
> - error_report("%s: unknown interrupt type", __func__);
> - abort();
> + /*
> + * Device is not configured with MSI/MSI-X yet, let's provide
> + * an empty message to make all device drivers happy.
> + */
> + memset(&msg, 0, sizeof(msg));
> }
> return msg;
> }
Looks like a hack to me. Even if callers happen to treat
0 message as a nop, there's no guarantee that's true for
all platforms. Pls change pci_get_msi_message to
return an error code, and fix callers to check that.
> --
> 2.7.4
