Il 12/05/2014 12:18, Michael S. Tsirkin ha scritto:
On Mon, May 12, 2014 at 12:14:25PM +0200, Paolo Bonzini wrote:
Il 12/05/2014 12:08, Michael S. Tsirkin ha scritto:
On Mon, May 12, 2014 at 11:57:32AM +0200, Paolo Bonzini wrote:
Perhaps we can check for cases where only the address is changing,
and poke at an existing struct kvm_kernel_irq_routing_entry without
doing any RCU synchronization?
I suspect interrupts can get lost then: e.g. if address didn't match any
cpus, now it matches some. No?
Can you explain the problem more verbosely? :)
Multiple writers would still be protected by the mutex, so you
cannot have an "in-place update" writer racing with a "copy the
array" writer.
I am not sure really.
I'm worried about reader vs writer.
If reader sees a stale msi value msi will be sent to a wrong
address.
That shouldn't happen on any cache-coherent system, no?
Or at least, it shouldn't become any worse than what can already happen
with RCU.
Paolo
