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Commit 105f8d40 authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: Calculate available entries in coalesced mmio ring 



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: default avatarAvi Kivity <avi@redhat.com>
parent 596ae895

virt/kvm/coalesced_mmio.c

+5 −5
Original line number Original line Diff line number Diff line
@@ -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_dev *dev = to_mmio(this);

	struct kvm_coalesced_mmio_zone *zone;

	struct kvm_coalesced_mmio_zone *zone;

	int next;

	struct kvm_coalesced_mmio_ring *ring;

	unsigned avail;

	int i;

	int i;





	if (!is_write)

	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

	 * check if we don't meet the first used entry

	 * there is always one unused entry in the buffer

	 * there is always one unused entry in the buffer

	 */

	 */



	ring = dev->kvm->coalesced_mmio_ring;

	next = (dev->kvm->coalesced_mmio_ring->last + 1) %

	avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;

							KVM_COALESCED_MMIO_MAX;

	if (avail < 1) {

	if (next == dev->kvm->coalesced_mmio_ring->first) {

		/* full */

		/* full */

		return 0;

		return 0;

	}

	}