On 01/20/2010 11:34 AM, Sheng Yang wrote:
I think we can even do this from the I/O thread, without stopping a
vcpu, since the colaesced mmio page is not tied to a vcpu but is a vm
property.
This one sounds better. But I've taken a look at the current userspace code:
#if defined(KVM_CAP_COALESCED_MMIO)
if (kvm_state->coalesced_mmio) {
struct kvm_coalesced_mmio_ring *ring =
(void *) run + kvm_state->coalesced_mmio * PAGE_SIZE;
while (ring->first != ring->last) {
cpu_physical_memory_rw(ring->coalesced_mmio[ring->first].phys_addr,
&ring->coalesced_mmio[ring->first].data[0],
ring->coalesced_mmio[ring->first].len, 1);
smp_wmb();
ring->first = (ring->first + 1) % KVM_COALESCED_MMIO_MAX;
}
}
#endif
No protection for ring->first and ring->last? Seems it can writing the same element pointed by
ring->first twice, then skip one element at (ring->first + 1)...
ring->first is owned by userspace, while ring->last is owned by the
kernel, so no protection is necessary except for the memory barrier.
Can you elaborate on how it would fail?
--
error compiling committee.c: too many arguments to function
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