These quirks are necessary for GeForce, but not for Quadro/GRID/Tesla
assignment. Leaving them enabled is fully functional and provides the
most compatibility, but due to the unique NVIDIA MSI ACK behavior[1],
it also introduces latency in re-triggering the MSI interrupt. This
overhead is typically negligible, but has been shown to adversely
affect some (very) high interrupt rate applications. This adds the
vfio-pci device option "x-no-geforce-quirks=" which can be set to
"on" to disable this additional overhead.
A follow-on optimization for GeForce might be to make use of an
ioeventfd to allow KVM to trigger an irqfd in the kernel vfio-pci
driver, avoiding the bounce through userspace to handle this device
write.
[1] Background: the NVIDIA driver has been observed to write 0xff to
the read-only MSI capability ID register via the MMIO mirror of PCI
config space in order for the MSI interrupt to re-trigger. This PCI
config space mirror is virtualized in QEMU for GeForce.
Signed-off-by: Alex Williamson <alex.william...@redhat.com>
---
hw/vfio/pci-quirks.c | 9 ++++++---
hw/vfio/pci.c | 2 ++
hw/vfio/pci.h | 1 +
3 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
index 60ad5fb91a83..e5779a7ad35b 100644
--- a/hw/vfio/pci-quirks.c
+++ b/hw/vfio/pci-quirks.c
@@ -542,7 +542,8 @@ static void vfio_vga_probe_nvidia_3d0_quirk(VFIOPCIDevice
*vdev)
VFIOQuirk *quirk;
VFIONvidia3d0Quirk *data;
- if (!vfio_pci_is(vdev, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID) ||
+ if (vdev->no_geforce_quirks ||
+ !vfio_pci_is(vdev, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID) ||
!vdev->bars[1].region.size) {
return;
}
@@ -660,7 +661,8 @@ static void vfio_probe_nvidia_bar5_quirk(VFIOPCIDevice
*vdev, int nr)
VFIONvidiaBAR5Quirk *bar5;
VFIOConfigWindowQuirk *window;
- if (!vfio_pci_is(vdev, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID) ||
+ if (vdev->no_geforce_quirks ||
+ !vfio_pci_is(vdev, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID) ||
!vdev->vga || nr != 5 || !vdev->bars[5].ioport) {
return;
}
@@ -754,7 +756,8 @@ static void vfio_probe_nvidia_bar0_quirk(VFIOPCIDevice
*vdev, int nr)
VFIOQuirk *quirk;
VFIOConfigMirrorQuirk *mirror;
- if (!vfio_pci_is(vdev, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID) ||
+ if (vdev->no_geforce_quirks ||
+ !vfio_pci_is(vdev, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID) ||
!vfio_is_vga(vdev) || nr != 0) {
return;
}
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 2c7129512563..6d260b92c1e1 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2989,6 +2989,8 @@ static Property vfio_pci_dev_properties[] = {
DEFINE_PROP_BOOL("x-no-kvm-intx", VFIOPCIDevice, no_kvm_intx, false),
DEFINE_PROP_BOOL("x-no-kvm-msi", VFIOPCIDevice, no_kvm_msi, false),
DEFINE_PROP_BOOL("x-no-kvm-msix", VFIOPCIDevice, no_kvm_msix, false),
+ DEFINE_PROP_BOOL("x-no-geforce-quirks", VFIOPCIDevice,
+ no_geforce_quirks, false),
DEFINE_PROP_UINT32("x-pci-vendor-id", VFIOPCIDevice, vendor_id,
PCI_ANY_ID),
DEFINE_PROP_UINT32("x-pci-device-id", VFIOPCIDevice, device_id,
PCI_ANY_ID),
DEFINE_PROP_UINT32("x-pci-sub-vendor-id", VFIOPCIDevice,
diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index a8fb3b34222c..7c55087a1c44 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -142,6 +142,7 @@ typedef struct VFIOPCIDevice {
bool no_kvm_intx;
bool no_kvm_msi;
bool no_kvm_msix;
+ bool no_geforce_quirks;
} VFIOPCIDevice;
uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
