On (Mon) 19 Dec 2011 [14:09:43], Zang Hongyong wrote: > 于 2011/12/16,星期五 17:39, Amit Shah 写道: > >On (Fri) 16 Dec 2011 [09:14:26], zanghongyong@xxxxxxxxxx wrote: > >>From: Hongyong Zang<zanghongyong@xxxxxxxxxx> > >> > >>In pci_enable_msix(), the guest's virtio-serial driver tries to set msi-x > >>with one vector per queue. But it fails and eventually all virtio-serial > >>ports share one MSI-X vector. Because every virtio-serial port has *two* > >>virtqueues, virtio-serial needs (port+1)*2 vectors other than (port+1). > >Ouch, good catch. > > > >One comment below: > > > >>This patch allows every virtqueue to have its own MSI-X vector. > >>(When the MSI-X vectors needed are more than MSIX_MAX_ENTRIES defined in > >>qemu: msix.c, all the queues still share one MSI-X vector as before.) > >> > >>Signed-off-by: Hongyong Zang<zanghongyong@xxxxxxxxxx> > >>--- > >> hw/virtio-pci.c | 5 ++++- > >> 1 files changed, 4 insertions(+), 1 deletions(-) > >> > >>diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c > >>index 77b75bc..2c9c6fb 100644 > >>--- a/hw/virtio-pci.c > >>+++ b/hw/virtio-pci.c > >>@@ -718,8 +718,11 @@ static int virtio_serial_init_pci(PCIDevice *pci_dev) > >> return -1; > >> } > >> vdev->nvectors = proxy->nvectors == DEV_NVECTORS_UNSPECIFIED > >>- ? proxy->serial.max_virtserial_ports + 1 > >>+ ? (proxy->serial.max_virtserial_ports + 1) * 2 > >> : proxy->nvectors; > >>+ /*msix.c: #define MSIX_MAX_ENTRIES 32*/ > >>+ if (vdev->nvectors> 32) > >>+ vdev->nvectors = 32; > >This change isn't needed: if the proxy->nvectors value exceeds the max > >allowed, virtio_init_pci() will end up using a shared vector instead > >of separate ones. > > > Hi Amit, > If the nvectors exceeds the max, msix_init() will return -EINVAL in QEMU, > and the front-end driver in Guest will use regular interrupt instead > of MSI-X. In that case, I believe msix_init() should be changed to attempt to share interrupts instead of drivers doing this by themselves. Amit -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
