On Mon, Jan 31, 2011 at 02:47:34PM -0700, Alex Williamson wrote:
> On Mon, 2011-01-31 at 23:19 +0200, Michael S. Tsirkin wrote:
> > When MSI is off, each interrupt needs to be bounced through the io
> > thread when it's set/cleared, so vhost-net causes more context switches and
> > higher CPU utilization than userspace virtio which handles networking in
> > the same thread.
> >
> > We'll need to fix this by adding level irq support in kvm irqfd,
> > for now disable vhost-net in these configurations.
> >
> > Added a vhostforce flag to force vhost-net back on.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> >
> > Untested, I'll send a pull request later after
> > some testing assuming we've resolved the
> > command line comments to everyone's satisfaction.
> >
> > Changes since v1:
> > added vhostforce to enable vhost for non-MSI guests
>
> I'm still not thrilled with the errno hack. If this is really a generic
> problem, we should better architect the set_guest_notifiers() callback,
> the force option feels like a band-aide.
> I'm still curious if we can't
> be more dynamic about how we setup the set_guest_notifiers() function
> pointer so it only gets set if (force || msix_enabled()) and we can
> limit some of the impact here to vhost. Thanks,
>
> Alex
I'm not entirely happy with the API either, but I'm sure
playing with the function pointer is not the solution
we are looking for:
msix is enabled/disabled dynamically. force is static but it is
something net backend knows about, virtio pci doesn't.
So I suspect modifying the callback on the fly will become
messy quite quickly.
Well, this API will be easy to tweak after the fact, there's a single
user after all.
> > hw/vhost.c | 16 +++++++++++-----
> > hw/vhost.h | 3 ++-
> > hw/vhost_net.c | 8 +++++---
> > hw/vhost_net.h | 2 +-
> > hw/virtio-net.c | 6 ++++--
> > hw/virtio-pci.c | 6 +++++-
> > hw/virtio.h | 4 +++-
> > net/tap.c | 6 ++++--
> > qemu-options.hx | 4 +++-
> > 9 files changed, 38 insertions(+), 17 deletions(-)
> >
> > diff --git a/hw/vhost.c b/hw/vhost.c
> > index 6082da2..72df75f 100644
> > --- a/hw/vhost.c
> > +++ b/hw/vhost.c
> > @@ -581,7 +581,7 @@ static void vhost_virtqueue_cleanup(struct vhost_dev *dev,
> > 0, virtio_queue_get_desc_size(vdev, idx));
> > }
> >
> > -int vhost_dev_init(struct vhost_dev *hdev, int devfd)
> > +int vhost_dev_init(struct vhost_dev *hdev, int devfd, bool force)
> > {
> > uint64_t features;
> > int r;
> > @@ -613,6 +613,7 @@ int vhost_dev_init(struct vhost_dev *hdev, int devfd)
> > hdev->log_enabled = false;
> > hdev->started = false;
> > cpu_register_phys_memory_client(&hdev->client);
> > + hdev->force = force;
> > return 0;
> > fail:
> > r = -errno;
> > @@ -636,9 +637,12 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
> > goto fail;
> > }
> >
> > - r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, true);
> > + r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, true,
> > + hdev->force);
> > if (r < 0) {
> > - fprintf(stderr, "Error binding guest notifier: %d\n", -r);
> > + if (r != -EVIRTIO_DISABLED) {
> > + fprintf(stderr, "Error binding guest notifier: %d\n", -r);
> > + }
> > goto fail_notifiers;
> > }
> >
> > @@ -686,7 +690,8 @@ fail_vq:
> > }
> > fail_mem:
> > fail_features:
> > - vdev->binding->set_guest_notifiers(vdev->binding_opaque, false);
> > + vdev->binding->set_guest_notifiers(vdev->binding_opaque, false,
> > + hdev->force);
> > fail_notifiers:
> > fail:
> > return r;
> > @@ -704,7 +709,8 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
> > }
> > vhost_client_sync_dirty_bitmap(&hdev->client, 0,
> > (target_phys_addr_t)~0x0ull);
> > - r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, false);
> > + r = vdev->binding->set_guest_notifiers(vdev->binding_opaque, false,
> > + hdev->force);
> > if (r < 0) {
> > fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", r);
> > fflush(stderr);
> > diff --git a/hw/vhost.h b/hw/vhost.h
> > index 86dd834..d5d4d86 100644
> > --- a/hw/vhost.h
> > +++ b/hw/vhost.h
> > @@ -38,9 +38,10 @@ struct vhost_dev {
> > bool log_enabled;
> > vhost_log_chunk_t *log;
> > unsigned long long log_size;
> > + bool force;
> > };
> >
> > -int vhost_dev_init(struct vhost_dev *hdev, int devfd);
> > +int vhost_dev_init(struct vhost_dev *hdev, int devfd, bool force);
> > void vhost_dev_cleanup(struct vhost_dev *hdev);
> > int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
> > void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
> > diff --git a/hw/vhost_net.c b/hw/vhost_net.c
> > index c068be1..4f57271 100644
> > --- a/hw/vhost_net.c
> > +++ b/hw/vhost_net.c
> > @@ -81,7 +81,8 @@ static int vhost_net_get_fd(VLANClientState *backend)
> > }
> > }
> >
> > -struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd)
> > +struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd,
> > + bool force)
> > {
> > int r;
> > struct vhost_net *net = qemu_malloc(sizeof *net);
> > @@ -98,7 +99,7 @@ struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd)
> > (1 << VHOST_NET_F_VIRTIO_NET_HDR);
> > net->backend = r;
> >
> > - r = vhost_dev_init(&net->dev, devfd);
> > + r = vhost_dev_init(&net->dev, devfd, force);
> > if (r < 0) {
> > goto fail;
> > }
> > @@ -188,7 +189,8 @@ void vhost_net_cleanup(struct vhost_net *net)
> > qemu_free(net);
> > }
> > #else
> > -struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd)
> > +struct vhost_net *vhost_net_init(VLANClientState *backend, int devfd,
> > + bool force)
> > {
> > return NULL;
> > }
> > diff --git a/hw/vhost_net.h b/hw/vhost_net.h
> > index 6c18ff7..8435094 100644
> > --- a/hw/vhost_net.h
> > +++ b/hw/vhost_net.h
> > @@ -6,7 +6,7 @@
> > struct vhost_net;
> > typedef struct vhost_net VHostNetState;
> >
> > -VHostNetState *vhost_net_init(VLANClientState *backend, int devfd);
> > +VHostNetState *vhost_net_init(VLANClientState *backend, int devfd, bool force);
> >
> > int vhost_net_start(VHostNetState *net, VirtIODevice *dev);
> > void vhost_net_stop(VHostNetState *net, VirtIODevice *dev);
> > diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> > index ccb3e63..5de3fee 100644
> > --- a/hw/virtio-net.c
> > +++ b/hw/virtio-net.c
> > @@ -121,8 +121,10 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
> > if (!n->vhost_started) {
> > int r = vhost_net_start(tap_get_vhost_net(n->nic->nc.peer), &n->vdev);
> > if (r < 0) {
> > - error_report("unable to start vhost net: %d: "
> > - "falling back on userspace virtio", -r);
> > + if (r != -EVIRTIO_DISABLED) {
> > + error_report("unable to start vhost net: %d: "
> > + "falling back on userspace virtio", -r);
> > + }
> > } else {
> > n->vhost_started = 1;
> > }
> > diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> > index d07ff97..c93ef11 100644
> > --- a/hw/virtio-pci.c
> > +++ b/hw/virtio-pci.c
> > @@ -595,12 +595,16 @@ static int virtio_pci_set_guest_notifier(void *opaque, int n, bool assign)
> > return 0;
> > }
> >
> > -static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
> > +static int virtio_pci_set_guest_notifiers(void *opaque, bool assign, bool force)
> > {
> > VirtIOPCIProxy *proxy = opaque;
> > VirtIODevice *vdev = proxy->vdev;
> > int r, n;
> >
> > + if (assign && !force && !msix_enabled(&proxy->pci_dev)) {
> > + return -EVIRTIO_DISABLED;
> > + }
> > +
> > for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
> > if (!virtio_queue_get_num(vdev, n)) {
> > break;
> > diff --git a/hw/virtio.h b/hw/virtio.h
> > index d8546d5..156c9a3 100644
> > --- a/hw/virtio.h
> > +++ b/hw/virtio.h
> > @@ -93,11 +93,13 @@ typedef struct {
> > int (*load_config)(void * opaque, QEMUFile *f);
> > int (*load_queue)(void * opaque, int n, QEMUFile *f);
> > unsigned (*get_features)(void * opaque);
> > - int (*set_guest_notifiers)(void * opaque, bool assigned);
> > + int (*set_guest_notifiers)(void * opaque, bool assigned, bool force);
> > int (*set_host_notifier)(void * opaque, int n, bool assigned);
> > void (*vmstate_change)(void * opaque, bool running);
> > } VirtIOBindings;
> >
> > +#define EVIRTIO_DISABLED ERANGE
> > +
> > #define VIRTIO_PCI_QUEUE_MAX 64
> >
> > #define VIRTIO_NO_VECTOR 0xffff
> > diff --git a/net/tap.c b/net/tap.c
> > index eada34a..b8cd252 100644
> > --- a/net/tap.c
> > +++ b/net/tap.c
> > @@ -491,8 +491,10 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan
> > }
> > }
> >
> > - if (qemu_opt_get_bool(opts, "vhost", !!qemu_opt_get(opts, "vhostfd"))) {
> > + if (qemu_opt_get_bool(opts, "vhost", !!qemu_opt_get(opts, "vhostfd") ||
> > + qemu_opt_get_bool(opts, "vhostforce", false))) {
> > int vhostfd, r;
> > + bool force = qemu_opt_get_bool(opts, "vhostforce", false);
> > if (qemu_opt_get(opts, "vhostfd")) {
> > r = net_handle_fd_param(mon, qemu_opt_get(opts, "vhostfd"));
> > if (r == -1) {
> > @@ -502,7 +504,7 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan
> > } else {
> > vhostfd = -1;
> > }
> > - s->vhost_net = vhost_net_init(&s->nc, vhostfd);
> > + s->vhost_net = vhost_net_init(&s->nc, vhostfd, force);
> > if (!s->vhost_net) {
> > error_report("vhost-net requested but could not be initialized");
> > return -1;
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 898561d..11c93a2 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -1050,7 +1050,7 @@ DEF("net", HAS_ARG, QEMU_OPTION_net,
> > "-net tap[,vlan=n][,name=str],ifname=name\n"
> > " connect the host TAP network interface to VLAN 'n'\n"
> > #else
> > - "-net tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off][,vhostfd=h]\n"
> > + "-net tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off][,vhostfd=h][,vhostforce=on|off]\n"
> > " connect the host TAP network interface to VLAN 'n' and use the\n"
> > " network scripts 'file' (default=" DEFAULT_NETWORK_SCRIPT ")\n"
> > " and 'dfile' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n"
> > @@ -1061,6 +1061,8 @@ DEF("net", HAS_ARG, QEMU_OPTION_net,
> > " use vnet_hdr=off to avoid enabling the IFF_VNET_HDR tap flag\n"
> > " use vnet_hdr=on to make the lack of IFF_VNET_HDR support an error condition\n"
> > " use vhost=on to enable experimental in kernel accelerator\n"
> > + " (only has effect for virtio guests which use MSIX)\n"
> > + " use vhostforce=on to force vhost on for non-MSIX virtio guests\n"
> > " use 'vhostfd=h' to connect to an already opened vhost net device\n"
> > #endif
> > "-net socket[,vlan=n][,name=str][,fd=h][,listen=[host]:port][,connect=host:port]\n"
>
>
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