kvm: Switch to unlocked PIO

Do not take the BQL before dispatching PIO requests of KVM VCPUs.
Instead, address_space_rw will do it if necessary. This enables
completely BQL-free PIO handling in KVM mode for upcoming devices with
fine-grained locking.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <1434646046-27150-8-git-send-email-pbonzini@redhat.com>

kvm-all.c

@@ -1804,13 +1804,12 @@ int kvm_cpu_exec(CPUState *cpu)
         switch (run->exit_reason) {
         case KVM_EXIT_IO:
             DPRINTF("handle_io\n");
-            qemu_mutex_lock_iothread();
+            /* Called outside BQL */
             kvm_handle_io(run->io.port, attrs,
                           (uint8_t *)run + run->io.data_offset,
                           run->io.direction,
                           run->io.size,
                           run->io.count);
-            qemu_mutex_unlock_iothread();
             ret = 0;
             break;
         case KVM_EXIT_MMIO: