On 2018-12-10 12:31:43 -0500, Michael S. Tsirkin wrote: > On Mon, Dec 10, 2018 at 11:15:48AM -0500, Venu Busireddy wrote: > > From: Si-Wei Liu <si-wei....@oracle.com> > > > > When a VF is hotplugged into the guest, datapath switching will be > > performed immediately, which is sub-optimal in terms of timing, and > > could end up with substantial network downtime. One of ways to shorten > > this downtime is to switch the datapath only after the VF is seen to get > > enabled by guest, indicated by the bus master bit in VF's PCI config > > space getting enabled. The FAILOVER_PRIMARY_CHANGED event is emitted > > at that time to indicate this condition. Then management stack can kick > > off datapath switching upon receiving the event. > > > > Signed-off-by: Si-Wei Liu <si-wei....@oracle.com> > > Signed-off-by: Venu Busireddy <venu.busire...@oracle.com> > > As management stacks can lose events, it's necessary > to also have a query command to check device status.
Thanks for the feedback. Implemented the changes, and posted v2: https://lists.oasis-open.org/archives/virtio-dev/201901/msg00046.html > > --- > > hw/vfio/pci.c | 57 > > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > qapi/net.json | 26 ++++++++++++++++++++++++++ > > 2 files changed, 83 insertions(+) > > > > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c > > index ce1f33c..ea24ca2 100644 > > --- a/hw/vfio/pci.c > > +++ b/hw/vfio/pci.c > > @@ -34,6 +34,7 @@ > > #include "pci.h" > > #include "trace.h" > > #include "qapi/error.h" > > +#include "qapi/qapi-events-net.h" > > > > #define MSIX_CAP_LENGTH 12 > > > > @@ -42,6 +43,7 @@ > > > > static void vfio_disable_interrupts(VFIOPCIDevice *vdev); > > static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled); > > +static void vfio_failover_notify(VFIOPCIDevice *vdev, bool status); > > > > /* > > * Disabling BAR mmaping can be slow, but toggling it around INTx can > > @@ -1170,6 +1172,8 @@ void vfio_pci_write_config(PCIDevice *pdev, > > { > > VFIOPCIDevice *vdev = PCI_VFIO(pdev); > > uint32_t val_le = cpu_to_le32(val); > > + bool may_notify = false; > > + bool master_was = false; > > > > trace_vfio_pci_write_config(vdev->vbasedev.name, addr, val, len); > > > > @@ -1180,6 +1184,14 @@ void vfio_pci_write_config(PCIDevice *pdev, > > __func__, vdev->vbasedev.name, addr, val, len); > > } > > > > + /* Bus Master Enabling/Disabling */ > > + if (pdev->failover_primary && current_cpu && > > + range_covers_byte(addr, len, PCI_COMMAND)) { > > + master_was = !!(pci_get_word(pdev->config + PCI_COMMAND) & > > + PCI_COMMAND_MASTER); > > + may_notify = true; > > + } > > + > > /* MSI/MSI-X Enabling/Disabling */ > > if (pdev->cap_present & QEMU_PCI_CAP_MSI && > > ranges_overlap(addr, len, pdev->msi_cap, vdev->msi_cap_size)) { > > @@ -1235,6 +1247,14 @@ void vfio_pci_write_config(PCIDevice *pdev, > > /* Write everything to QEMU to keep emulated bits correct */ > > pci_default_write_config(pdev, addr, val, len); > > } > > + > > + if (may_notify) { > > + bool master_now = !!(pci_get_word(pdev->config + PCI_COMMAND) & > > + PCI_COMMAND_MASTER); > > + if (master_was != master_now) { > > + vfio_failover_notify(vdev, master_now); > > + } > > + } > > } > > > > /* > > It's very easy to have guest trigger a high load of events by playing > with the bus master enable bits. How about instead sending an event > that just says "something changed" without the current status and have > management issue a query command to check the status. QEMU then does not > need to re-send an event until management issues a query command. > > > > @@ -2801,6 +2821,17 @@ static void > > vfio_unregister_req_notifier(VFIOPCIDevice *vdev) > > vdev->req_enabled = false; > > } > > > > +static void vfio_failover_notify(VFIOPCIDevice *vdev, bool status) > > +{ > > + PCIDevice *pdev = &vdev->pdev; > > + const char *n; > > + gchar *path; > > + > > + n = pdev->qdev.id ? pdev->qdev.id : vdev->vbasedev.name; > > + path = object_get_canonical_path(OBJECT(vdev)); > > + qapi_event_send_failover_primary_changed(!!n, n, path, status); > > +} > > + > > static void vfio_realize(PCIDevice *pdev, Error **errp) > > { > > VFIOPCIDevice *vdev = PCI_VFIO(pdev); > > @@ -3109,10 +3140,36 @@ static void vfio_instance_finalize(Object *obj) > > vfio_put_group(group); > > } > > > > +static void vfio_exit_failover_notify(VFIOPCIDevice *vdev) > > +{ > > + PCIDevice *pdev = &vdev->pdev; > > + > > + /* > > + * Guest driver may not get the chance to disable bus mastering > > + * before the device object gets to be unrealized. In that event, > > + * send out a "disabled" notification on behalf of guest driver. > > + */ > > + if (pdev->failover_primary && > > + pdev->bus_master_enable_region.enabled) { > > + vfio_failover_notify(vdev, false); > > + } > > +} > > + > > With the idea above this won't be necessary anymore. > > > > static void vfio_exitfn(PCIDevice *pdev) > > { > > VFIOPCIDevice *vdev = PCI_VFIO(pdev); > > > > + /* > > + * During the guest reboot sequence, it is sometimes possible that > > + * the guest may not get sufficient time to complete the entire driver > > + * removal sequence, near the end of which a PCI config space write to > > + * disable bus mastering can be intercepted by device. In such cases, > > + * the FAILOVER_PRIMARY_CHANGED "disable" event will not be emitted. It > > + * is imperative to generate the event on the guest's behalf if the > > + * guest fails to make it. > > + */ > > + vfio_exit_failover_notify(vdev); > > + > > vfio_unregister_req_notifier(vdev); > > vfio_unregister_err_notifier(vdev); > > pci_device_set_intx_routing_notifier(&vdev->pdev, NULL); > > diff --git a/qapi/net.json b/qapi/net.json > > index 04a9de9..e5992c8 100644 > > --- a/qapi/net.json > > +++ b/qapi/net.json > > @@ -727,3 +727,29 @@ > > ## > > { 'event': 'FAILOVER_UNPLUG_PRIMARY', > > 'data': {'*device': 'str', 'path': 'str'} } > > + > > +## > > +# @FAILOVER_PRIMARY_CHANGED: > > +# > > +# Emitted whenever the driver of failover primary is loaded or unloaded > > +# by the guest. > > +# > > +# @device: device name > > +# > > +# @path: device path > > +# > > +# @enabled: true if driver is loaded thus device is enabled in guest > > +# > > +# Since: 3.0 > > +# > > +# Example: > > +# > > +# <- { "event": "FAILOVER_PRIMARY_CHANGED", > > > This event doesn't seem to be failover specific. > How about a more generic name? > > > > > +# "data": { "device": "vfio-0", > > +# "path": "/machine/peripheral/vfio-0" }, > > +# "enabled": "true" }, > > +# "timestamp": { "seconds": 1539935213, "microseconds": 753529 } } > > +# > > +## > > +{ 'event': 'FAILOVER_PRIMARY_CHANGED', > > + 'data': { '*device': 'str', 'path': 'str', 'enabled': 'bool' } } > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org >