Instead of checking whether we'll wrap around, calculate how many entries are available, and check whether we have enough (just one) for the pending mmio. By itself, this doesn't change anything, but it paves the way for making this function lockless. Signed-off-by: Avi Kivity <avi@xxxxxxxxxx> --- virt/kvm/coalesced_mmio.c | 10 +++++----- 1 files changed, 5 insertions(+), 5 deletions(-) diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c index c4c7ec2..7549068 100644 --- a/virt/kvm/coalesced_mmio.c +++ b/virt/kvm/coalesced_mmio.c @@ -24,7 +24,8 @@ static int coalesced_mmio_in_range(struct kvm_io_device *this, { struct kvm_coalesced_mmio_dev *dev = to_mmio(this); struct kvm_coalesced_mmio_zone *zone; - int next; + struct kvm_coalesced_mmio_ring *ring; + unsigned avail; int i; if (!is_write) @@ -40,10 +41,9 @@ static int coalesced_mmio_in_range(struct kvm_io_device *this, * check if we don't meet the first used entry * there is always one unused entry in the buffer */ - - next = (dev->kvm->coalesced_mmio_ring->last + 1) % - KVM_COALESCED_MMIO_MAX; - if (next == dev->kvm->coalesced_mmio_ring->first) { + ring = dev->kvm->coalesced_mmio_ring; + avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX; + if (avail < 1) { /* full */ return 0; } -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html