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vhost: force vhost off for non-MSI guests

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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@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
mst@redhat.com 2011-02-01 22:13:42 +02:00 • committed by Anthony Liguori
parent f157ed202e
commit 5430a28fe4
9 changed files with 52 additions and 13 deletions
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6
net/tap.c
View file

@ -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;