On Sat, Apr 19, 2014 at 12:08:15PM +0800, Amos Kong wrote: > > Hi all, > > I'm working on this item in Upstream Networking todolist: > > | - Sharing config interrupts > | Support more devices by sharing a single msi vector > | between multiple virtio devices. > | (Applies to virtio-blk too). > > I have this solution here, and only have draft patches of Solution > 1 & 2, let's discuss if solution 3 is feasible. > > * We should not introduce perf regression in this change > * little effect is acceptable because we are _sharing_ interrupt > > Solution 1: > ========== > share one LSI interrupt for configuration change of all virtio devices. > Draft patch: share_lsi_for_all_config.patch > > Solution 2: > ========== > share one MSI interrupt for configuration change of all virtio devices. > Draft patch: share_msix_for_all_config.patch > > Solution 3: > ========== > dynamic adjust interrupt policy when device is added or removed > Current: > ------- > - try to allocate a MSI to device's config > - try to allocate a MSI for each vq > - share one MSI for all vqs of one device > - share one LSI for config & vqs of one device > > additional dynamic policies: > --------------------------- > - if there is no enough MSI, adjust interrupt allocation for returning > some MSI > - try to find a device that allocated one MSI for each vq, change > it to share one MSI for saving the MSI > - try to share one MSI for config of all virtio_pci devices > - try to share one LSI for config of all devices > > - if device is removed, try to re-allocate freed MSI to existed > devices, if they aren't in best status (one MSI for config, one > MSI for each vq) > - if config of all devices is sharing one LSI, try to upgrade it to MSI > - if config of all devices is sharing one MSI, try to allocate one > MSI for configuration change of each device > - try to find a device that is sharing one MSI for all vqs, try to > allocate one MSI for each vq > > > > BTW, I saw we still notify all vqs even VIRTIO_PCI_ISR_CONFIG bit of > isr is set, is it necessary? [Reply myself] Quote from Virtio-spec: | 2.4.3 Dealing With Configuration Changes | Some virtio PCI devices can change the device configuration state, as reflected | in the virtio header in the PCI configuration space. In this case: | | 1. If MSI-X capability is disabled: an interrupt is delivered and the sec- | ond highest bit is set in the ISR Status field to indicate that the driver | should re-examine the configuration space. | Note that a single interrupt can | indicate both that one or more virtqueue has been used and that the con- | figuration space has changed: even if the config bit is set, virtqueues must | be scanned. <<<< It seems current code is fine. > diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c > index 101db3f..176aabc 100644 > --- a/drivers/virtio/virtio_pci.c > +++ b/drivers/virtio/virtio_pci.c > @@ -259,9 +259,9 @@ static irqreturn_t vp_interrupt(int irq, void > *opaque) > > /* Configuration change? Tell driver if it wants to know. */ > if (isr & VIRTIO_PCI_ISR_CONFIG) > - vp_config_changed(irq, opaque); > - > - return vp_vring_interrupt(irq, opaque); > + return vp_config_changed(irq, opaque); > + else > + return vp_vring_interrupt(irq, opaque); > } > > static void vp_free_vectors(struct virtio_device *vdev) > > -- > Amos. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
