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| author | Stefan Hajnoczi | 2011-01-25 17:17:14 +0100 |
|---|---|---|
| committer | Kevin Wolf | 2011-01-31 10:03:00 +0100 |
| commit | d0dcac833a767dade968a07aba4d116f162ebc72 (patch) | |
| tree | 44424b95b63e18b1dc4bca9c40739664d959aa86 /kvm-all.c | |
| parent | virtio-blk: tell the guest about size changes (diff) | |
| download | qemu-d0dcac833a767dade968a07aba4d116f162ebc72.tar.gz qemu-d0dcac833a767dade968a07aba4d116f162ebc72.tar.xz qemu-d0dcac833a767dade968a07aba4d116f162ebc72.zip | |
virtio-pci: Disable virtio-ioeventfd when !CONFIG_IOTHREAD
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>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'kvm-all.c')
| -rw-r--r-- | kvm-all.c | 8 |
1 files changed, 6 insertions, 2 deletions
@@ -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++) { |