[PATCH v2 1/2] KVM: MMIO: Lock coalesced device when checking for available entry

Sasha Levin
2011-07-15T11:38:58Z

Move the check whether there are available entries to within the spinlock.
This allows working with larger amount of VCPUs and reduces premature
exits when using a large number of VCPUs.

Cc: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
virt/kvm/coalesced_mmio.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index fc84875..34188db 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -37,7 +37,7 @@ static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
*/
ring = dev->kvm->coalesced_mmio_ring;
avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
- if (avail < KVM_MAX_VCPUS) {
+ if (avail == 0) {
/* full */
return 0;
}
@@ -63,11 +63,14 @@ static int coalesced_mmio_write(struct kvm_io_device *this,
{
struct kvm_coalesced_mmio_dev *dev = to_mmio(this);
struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
- if (!coalesced_mmio_in_range(dev, addr, len))
- return -EOPNOTSUPP;

spin_lock(&dev->lock);

+ if (!coalesced_mmio_in_range(dev, addr, len)) {
+ spin_unlock(&dev->lock);
+ return -EOPNOTSUPP;
+ }
+
/* copy data in first free entry of the ring */

ring->coalesced_mmio[ring->last].phys_addr = addr;
--
1.7.6