Re: [PATCH v2] s390x/pci: set kvm_msi_via_irqfd_allowed

[Farhan Ali <alifm@linux.ibm.com>]

Reviewed-by: Farhan Ali <alifm@linux.ibm.com>

On 10/7/2025 1:56 PM, Matthew Rosato wrote:
> Allow irqfd to be used for virtio-pci on s390x if the kernel supports
> it.  This improves s390x virtio-pci performance when using kvm
> acceleration by allowing kvm to deliver interrupts instead of QEMU.
>
> Reviewed-by: Eric Farman <farman@linux.ibm.com>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> v2:
>   - add review tag
>   - tweak commit message (David)
> ---
>   hw/s390x/s390-pci-bus.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
> index e8e41c8a9a..88852acf45 100644
> --- a/hw/s390x/s390-pci-bus.c
> +++ b/hw/s390x/s390-pci-bus.c
> @@ -900,6 +900,7 @@ static void s390_pcihost_realize(DeviceState *dev, Error **errp)
>       s390_pci_init_default_group();
>       css_register_io_adapters(CSS_IO_ADAPTER_PCI, true, false,
>                                S390_ADAPTER_SUPPRESSIBLE, errp);
> +    kvm_msi_via_irqfd_allowed = kvm_irqfds_enabled();
>   }
>   
>   static void s390_pcihost_unrealize(DeviceState *dev)