| Message ID | 1295972234-1287-1-git-send-email-stefanha@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jan 25, 2011 at 04:17:14PM +0000, Stefan Hajnoczi wrote: > It is not possible to use virtio-ioeventfd when building without an I/O > thread. We rely on a signal to kick us out of vcpu execution. Timers > and AIO use SIGALRM and SIGUSR2 respectively. Unfortunately eventfd > does not support O_ASYNC (SIGIO) so eventfd cannot be used in a signal > driven manner. > > Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> > --- > kvm-all.c | 8 ++++++-- > 1 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/kvm-all.c b/kvm-all.c > index 255b6fa..8f0e17c 100644 > --- a/kvm-all.c > +++ b/kvm-all.c > @@ -449,10 +449,14 @@ int kvm_check_extension(KVMState *s, unsigned int extension) > > static int kvm_check_many_ioeventfds(void) > { > - /* Older kernels have a 6 device limit on the KVM io bus. Find out so we > + /* Userspace can use ioeventfd for io notification. This requires a host > + * that supports eventfd(2) and an I/O thread; since eventfd does not > + * support SIGIO it cannot interrupt the vcpu. > + * > + * Older kernels have a 6 device limit on the KVM io bus. Find out so we > * can avoid creating too many ioeventfds. > */ > -#ifdef CONFIG_EVENTFD > +#if defined(CONFIG_EVENTFD) && defined(CONFIG_IOTHREAD) > int ioeventfds[7]; > int i, ret = 0; > for (i = 0; i < ARRAY_SIZE(ioeventfds); i++) { > -- > 1.7.2.3
Am 25.01.2011 18:42, schrieb Michael S. Tsirkin: > On Tue, Jan 25, 2011 at 04:17:14PM +0000, Stefan Hajnoczi wrote: >> It is not possible to use virtio-ioeventfd when building without an I/O >> thread. We rely on a signal to kick us out of vcpu execution. Timers >> and AIO use SIGALRM and SIGUSR2 respectively. Unfortunately eventfd >> does not support O_ASYNC (SIGIO) so eventfd cannot be used in a signal >> driven manner. >> >> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> > > Acked-by: Michael S. Tsirkin <mst@redhat.com> I guess this means that it should go through my tree? I applied it to the block branch now. Kevin
diff --git a/kvm-all.c b/kvm-all.c index 255b6fa..8f0e17c 100644 --- a/kvm-all.c +++ b/kvm-all.c @@ -449,10 +449,14 @@ int kvm_check_extension(KVMState *s, unsigned int extension) static int kvm_check_many_ioeventfds(void) { - /* Older kernels have a 6 device limit on the KVM io bus. Find out so we + /* Userspace can use ioeventfd for io notification. This requires a host + * that supports eventfd(2) and an I/O thread; since eventfd does not + * support SIGIO it cannot interrupt the vcpu. + * + * Older kernels have a 6 device limit on the KVM io bus. Find out so we * can avoid creating too many ioeventfds. */ -#ifdef CONFIG_EVENTFD +#if defined(CONFIG_EVENTFD) && defined(CONFIG_IOTHREAD) int ioeventfds[7]; int i, ret = 0; for (i = 0; i < ARRAY_SIZE(ioeventfds); i++) {
It is not possible to use virtio-ioeventfd when building without an I/O thread. We rely on a signal to kick us out of vcpu execution. Timers and AIO use SIGALRM and SIGUSR2 respectively. Unfortunately eventfd does not support O_ASYNC (SIGIO) so eventfd cannot be used in a signal driven manner. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> --- kvm-all.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-)