[Qemu-devel] [PATCH 13/18] kvm: Unconditionally reenter kernel after IO exits

[Jan Kiszka]

From: Jan Kiszka <address@hidden>

KVM requires to reenter the kernel after IO exits in order to complete
instruction emulation. Failing to do so will leave the kernel state
inconsistently behind. To ensure that we will get back ASAP, we issue a
self-signal that will cause KVM_RUN to return once the pending
operations are completed.

This patch also fixes the missing exit_request check in kvm_cpu_exec in
the CONFIG_IOTHREAD case.

Signed-off-by: Jan Kiszka <address@hidden>
CC: Gleb Natapov <address@hidden>
---
 kvm-all.c |   20 +++++++++++---------
 1 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/kvm-all.c b/kvm-all.c
index f3c8375..429ab7a 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -188,7 +188,6 @@ int kvm_pit_in_kernel(void)
     return kvm_state.pit_in_kernel;
 }
 
-
 int kvm_init_vcpu(CPUState *env)
 {
     long mmap_size;
@@ -831,23 +830,26 @@ int kvm_cpu_exec(CPUState *env)
     }
 
     do {
-#ifndef CONFIG_IOTHREAD
-        if (env->exit_request) {
-            DPRINTF("interrupt exit requested\n");
-            ret = 0;
-            break;
-        }
-#endif
-
         if (env->kvm_vcpu_dirty) {
             kvm_arch_put_registers(env, KVM_PUT_RUNTIME_STATE);
             env->kvm_vcpu_dirty = 0;
         }
 
         kvm_arch_pre_run(env, run);
+        if (env->exit_request) {
+            DPRINTF("interrupt exit requested\n");
+            /*
+             * KVM requires us to reenter the kernel after IO exits to complete
+             * instruction emulation. This self-signal will ensure that we
+             * leave ASAP again.
+             */
+            qemu_cpu_kick_self();
+        }
         cpu_single_env = NULL;
         qemu_mutex_unlock_iothread();
+
         ret = kvm_vcpu_ioctl(env, KVM_RUN, 0);
+
         qemu_mutex_lock_iothread();
         cpu_single_env = env;
         kvm_arch_post_run(env, run);
-- 
1.7.1