Re: [Qemu-devel] [PATCH v5] vhost-user interrupt management fixes

[Michael S. Tsirkin]

On Fri, Feb 19, 2016 at 10:02:16AM +0100, Didier Pallard wrote:
> Hi victor,
> 
> I'm sorry, i didn't get time to work on this patch.
> Thanks for your work.
> 
> didier

Could you please confirm that the patch works for you?

> 
> On 02/18/2016 03:12 PM, Victor Kaplansky wrote:
> >Since guest_mask_notifier can not be used in vhost-user mode due
> >to buffering implied by unix control socket, force
> >use_mask_notifier on virtio devices of vhost-user interfaces, and
> >send correct callfd to the guest at vhost start.
> >
> >Using guest_notifier_mask function in vhost-user case may
> >break interrupt mask paradigm, because mask/unmask is not
> >really done when returning from guest_notifier_mask call, instead
> >message is posted in a unix socket, and processed later.
> >
> >Add an option boolean flag 'use_mask_notifier' to disable the use
> >of guest_notifier_mask in virtio pci.
> >
> >Signed-off-by: Didier Pallard <address@hidden>
> >Signed-off-by: Victor Kaplansky <address@hidden>
> >---
> >v5 changes:
> >   - rebased to mst tree.
> >   - removed a traling space.
> >
> >v4 changes:
> >  In respond to Michael S. Tsirkin comments:
> >    - changed the name of new field to use_guest_notifier_mask
> >    - clarified comments
> >    - vhost_virtqueue_mask() called for unmask
> >    - cosmetic changes
> >    - moved the initialization of the new field from virtio_reset
> >      to virtio_init.
> >
> >v3 changes:
> >  In respond to Michael S. Tsirkin comments:
> >    - vhost_net.c: removed dependency on virtio-pci.h
> >    - vhost.c: simplified the check for vhost-user backend,
> >      replaced by checking use_mask_notifier; added comment
> >      explaining why vring for vhost-user initialized in
> >      unmasked state;
> >    - cosmetic fixes.
> >
> >v2 changes:
> >  - a new boolean field is added to all virtio devices instead
> >    of defining a property in some virtio-pci devices.
> >
> >  include/hw/virtio/virtio.h |  1 +
> >  hw/net/vhost_net.c         | 15 +++++++++++++--
> >  hw/virtio/vhost.c          |  9 +++++++++
> >  hw/virtio/virtio-pci.c     | 14 ++++++++------
> >  hw/virtio/virtio.c         |  1 +
> >  5 files changed, 32 insertions(+), 8 deletions(-)
> >
> >diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >index 108cdb0f..c38a2fef 100644
> >--- a/include/hw/virtio/virtio.h
> >+++ b/include/hw/virtio/virtio.h
> >@@ -90,6 +90,7 @@ struct VirtIODevice
> >      VMChangeStateEntry *vmstate;
> >      char *bus_name;
> >      uint8_t device_endian;
> >+    bool use_guest_notifier_mask;
> >      QLIST_HEAD(, VirtQueue) *vector_queues;
> >  };
> >diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> >index b2428324..6e1032fc 100644
> >--- a/hw/net/vhost_net.c
> >+++ b/hw/net/vhost_net.c
> >@@ -284,8 +284,19 @@ int vhost_net_start(VirtIODevice *dev, NetClientState 
> >*ncs,
> >      }
> >      for (i = 0; i < total_queues; i++) {
> >-        vhost_net_set_vq_index(get_vhost_net(ncs[i].peer), i * 2);
> >-    }
> >+        struct vhost_net *net;
> >+
> >+        net = get_vhost_net(ncs[i].peer);
> >+        vhost_net_set_vq_index(net, i * 2);
> >+
> >+        /* Suppress the masking guest notifiers on vhost user
> >+         * because vhost user doesn't interrupt masking/unmasking
> >+         * properly.
> >+         */
> >+        if (net->nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
> >+                dev->use_guest_notifier_mask = false;
> >+        }
> >+     }
> >      r = k->set_guest_notifiers(qbus->parent, total_queues * 2, true);
> >      if (r < 0) {
> >diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> >index 9f8ac38c..72d0c9e9 100644
> >--- a/hw/virtio/vhost.c
> >+++ b/hw/virtio/vhost.c
> >@@ -875,6 +875,14 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
> >      /* Clear and discard previous events if any. */
> >      event_notifier_test_and_clear(&vq->masked_notifier);
> >+    /* Init vring in unmasked state, unless guest_notifier_mask
> >+     * will do it later.
> >+     */
> >+    if (!vdev->use_guest_notifier_mask) {
> >+        /* TODO: check and handle errors. */
> >+        vhost_virtqueue_mask(dev, vdev, idx, false);
> >+    }
> >+
> >      return 0;
> >  fail_kick:
> >@@ -1167,6 +1175,7 @@ void vhost_virtqueue_mask(struct vhost_dev *hdev, 
> >VirtIODevice *vdev, int n,
> >      struct vhost_vring_file file;
> >      if (mask) {
> >+        assert(vdev->use_guest_notifier_mask);
> >          file.fd = event_notifier_get_fd(&hdev->vqs[index].masked_notifier);
> >      } else {
> >          file.fd = 
> > event_notifier_get_fd(virtio_queue_get_guest_notifier(vvq));
> >diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> >index 5494ff4a..440776c0 100644
> >--- a/hw/virtio/virtio-pci.c
> >+++ b/hw/virtio/virtio-pci.c
> >@@ -806,7 +806,7 @@ static int kvm_virtio_pci_vector_use(VirtIOPCIProxy 
> >*proxy, int nvqs)
> >          /* If guest supports masking, set up irqfd now.
> >           * Otherwise, delay until unmasked in the frontend.
> >           */
> >-        if (k->guest_notifier_mask) {
> >+        if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
> >              ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector);
> >              if (ret < 0) {
> >                  kvm_virtio_pci_vq_vector_release(proxy, vector);
> >@@ -822,7 +822,7 @@ undo:
> >          if (vector >= msix_nr_vectors_allocated(dev)) {
> >              continue;
> >          }
> >-        if (k->guest_notifier_mask) {
> >+        if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
> >              kvm_virtio_pci_irqfd_release(proxy, queue_no, vector);
> >          }
> >          kvm_virtio_pci_vq_vector_release(proxy, vector);
> >@@ -849,7 +849,7 @@ static void kvm_virtio_pci_vector_release(VirtIOPCIProxy 
> >*proxy, int nvqs)
> >          /* If guest supports masking, clean up irqfd now.
> >           * Otherwise, it was cleaned when masked in the frontend.
> >           */
> >-        if (k->guest_notifier_mask) {
> >+        if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
> >              kvm_virtio_pci_irqfd_release(proxy, queue_no, vector);
> >          }
> >          kvm_virtio_pci_vq_vector_release(proxy, vector);
> >@@ -882,7 +882,7 @@ static int virtio_pci_vq_vector_unmask(VirtIOPCIProxy 
> >*proxy,
> >      /* If guest supports masking, irqfd is already setup, unmask it.
> >       * Otherwise, set it up now.
> >       */
> >-    if (k->guest_notifier_mask) {
> >+    if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
> >          k->guest_notifier_mask(vdev, queue_no, false);
> >          /* Test after unmasking to avoid losing events. */
> >          if (k->guest_notifier_pending &&
> >@@ -905,7 +905,7 @@ static void virtio_pci_vq_vector_mask(VirtIOPCIProxy 
> >*proxy,
> >      /* If guest supports masking, keep irqfd but mask it.
> >       * Otherwise, clean it up now.
> >       */
> >-    if (k->guest_notifier_mask) {
> >+    if (vdev->use_guest_notifier_mask && k->guest_notifier_mask) {
> >          k->guest_notifier_mask(vdev, queue_no, true);
> >      } else {
> >          kvm_virtio_pci_irqfd_release(proxy, queue_no, vector);
> >@@ -1022,7 +1022,9 @@ static int virtio_pci_set_guest_notifier(DeviceState 
> >*d, int n, bool assign,
> >          event_notifier_cleanup(notifier);
> >      }
> >-    if (!msix_enabled(&proxy->pci_dev) && vdc->guest_notifier_mask) {
> >+    if (!msix_enabled(&proxy->pci_dev) &&
> >+        vdev->use_guest_notifier_mask &&
> >+        vdc->guest_notifier_mask) {
> >          vdc->guest_notifier_mask(vdev, n, !assign);
> >      }
> >diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >index 90f25451..e365960b 100644
> >--- a/hw/virtio/virtio.c
> >+++ b/hw/virtio/virtio.c
> >@@ -1677,6 +1677,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
> >      vdev->vmstate = qemu_add_vm_change_state_handler(virtio_vmstate_change,
> >                                                       vdev);
> >      vdev->device_endian = virtio_default_endian();
> >+    vdev->use_guest_notifier_mask = true;
> >  }
> >  hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)