kvm: First step to push iothread lock out of inner run loop

This opens the path to get rid of the iothread lock on vmexits in KVM
mode. On x86, the in-kernel irqchips has to be used because we otherwise
need to synchronize APIC and other per-cpu state accesses that could be
changed concurrently.

Regarding pre/post-run callbacks, s390x and ARM should be fine without
specific locking as the callbacks are empty. MIPS and POWER require
locking for the pre-run callback.

For the handle_exit callback, it is non-empty in x86, POWER and s390.
Some POWER cases could do without the locking, but it is left in
place for now.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1434646046-27150-7-git-send-email-pbonzini@redhat.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/kvm-all.c b/kvm-all.c
index e98b08def2..ca428ca298 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1755,6 +1755,8 @@ int kvm_cpu_exec(CPUState *cpu)
         return EXCP_HLT;
     }
 
+    qemu_mutex_unlock_iothread();
+
     do {
         MemTxAttrs attrs;
 
@@ -1773,11 +1775,9 @@ int kvm_cpu_exec(CPUState *cpu)
              */
             qemu_cpu_kick_self();
         }
-        qemu_mutex_unlock_iothread();
 
         run_ret = kvm_vcpu_ioctl(cpu, KVM_RUN, 0);
 
-        qemu_mutex_lock_iothread();
         attrs = kvm_arch_post_run(cpu, run);
 
         if (run_ret < 0) {
@@ -1804,20 +1804,24 @@ int kvm_cpu_exec(CPUState *cpu)
         switch (run->exit_reason) {
         case KVM_EXIT_IO:
             DPRINTF("handle_io\n");
+            qemu_mutex_lock_iothread();
             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:
             DPRINTF("handle_mmio\n");
+            qemu_mutex_lock_iothread();
             address_space_rw(&address_space_memory,
                              run->mmio.phys_addr, attrs,
                              run->mmio.data,
                              run->mmio.len,
                              run->mmio.is_write);
+            qemu_mutex_unlock_iothread();
             ret = 0;
             break;
         case KVM_EXIT_IRQ_WINDOW_OPEN:
@@ -1860,6 +1864,8 @@ int kvm_cpu_exec(CPUState *cpu)
         }
     } while (ret == 0);
 
+    qemu_mutex_lock_iothread();
+
     if (ret < 0) {
         cpu_dump_state(cpu, stderr, fprintf, CPU_DUMP_CODE);
         vm_stop(RUN_STATE_INTERNAL_ERROR);