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KVM: MMIO: Lock coalesced device when checking for available entry

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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>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Sasha Levin 2011-07-18 17:17:14 +03:00 committed by Avi Kivity
parent 22388a3c8c
commit c298125f4b
1 changed files with 27 additions and 15 deletions
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42
virt/kvm/coalesced_mmio.c
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@ -25,23 +25,8 @@ static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
gpa_t addr, int len)
{
struct kvm_coalesced_mmio_zone *zone;
struct kvm_coalesced_mmio_ring *ring;
unsigned avail;
int i;
/* Are we able to batch it ? */
/* last is the first free entry
* check if we don't meet the first used entry
* there is always one unused entry in the buffer
*/
ring = dev->kvm->coalesced_mmio_ring;
avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
if (avail < KVM_MAX_VCPUS) {
/* full */
return 0;
}
/* is it in a batchable area ? */
for (i = 0; i < dev->nb_zones; i++) {
@ -58,16 +43,43 @@ static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
return 0;
}
static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev)
{
struct kvm_coalesced_mmio_ring *ring;
unsigned avail;
/* Are we able to batch it ? */
/* last is the first free entry
* check if we don't meet the first used entry
* there is always one unused entry in the buffer
*/
ring = dev->kvm->coalesced_mmio_ring;
avail = (ring->first - ring->last - 1) % KVM_COALESCED_MMIO_MAX;
if (avail == 0) {
/* full */
return 0;
}
return 1;
}
static int coalesced_mmio_write(struct kvm_io_device *this,
gpa_t addr, int len, const void *val)
{
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_has_room(dev)) {
spin_unlock(&dev->lock);
return -EOPNOTSUPP;
}
/* copy data in first free entry of the ring */
ring->coalesced_mmio[ring->last].phys_addr = addr;