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s390x/pci: set kvm_msi_via_irqfd_allowed

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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.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Message-ID: <20251008203350.354121-1-mjrosato@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
Matthew Rosato 2025-10-08 16:33:50 -04:00 • committed by Thomas Huth
parent 00457aed51
commit 47ea726370
2 changed files with 8 additions and 0 deletions
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1
hw/s390x/s390-pci-bus.c
View file

@ -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);
s390_pcihost_kvm_realize();
}
static void s390_pcihost_unrealize(DeviceState *dev)

7
include/hw/s390x/s390-pci-kvm.h
View file

@ -14,12 +14,19 @@
#include "hw/s390x/s390-pci-bus.h"
#include "hw/s390x/s390-pci-inst.h"
#include "system/kvm.h"
#ifdef CONFIG_KVM
static inline void s390_pcihost_kvm_realize(void)
{
kvm_msi_via_irqfd_allowed = kvm_irqfds_enabled();
}
bool s390_pci_kvm_interp_allowed(void);
int s390_pci_kvm_aif_enable(S390PCIBusDevice *pbdev, ZpciFib *fib, bool assist);
int s390_pci_kvm_aif_disable(S390PCIBusDevice *pbdev);
#else
static inline void s390_pcihost_kvm_realize(void) {}
static inline bool s390_pci_kvm_interp_allowed(void)
{
return false;