[Qemu-devel] [PATCH] introduce on_vcpu

[Glauber Costa <glommer@redhat.com>]

on_vcpu is a qemu-kvm function that will make sure that a specific
piece of code will run on a requested cpu. We don't need that because
we're restricted to -smp 1 right now, but those days are likely to end soon.

So for the benefit of having qemu-kvm share more code with us, I'm
introducing our own version of on_vcpu(). Right now, we either run
a function on the current cpu, or abort the execution, because it would
mean something is seriously wrong.

As an example code, I "ported" kvm_update_guest_debug to use it,
with some slight differences from qemu-kvm.

This is probably 0.12 material

Signed-off-by: Glauber Costa <glommer@redhat.com>
CC: Jan Kiszka <jan.kiszka@siemens.com>
---
 kvm-all.c |   37 +++++++++++++++++++++++++++++++------
 1 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/kvm-all.c b/kvm-all.c
index 4e913e5..1d91f2e 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -39,6 +39,8 @@
     do { } while (0)
 #endif
 
+CPUState *current_env;
+
 typedef struct KVMSlot
 {
     target_phys_addr_t start_addr;
@@ -145,6 +147,14 @@ static int kvm_set_user_memory_region(KVMState *s, KVMSlot *slot)
     return kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
 }
 
+static void on_vcpu(CPUState *env, void (*func)(void *data), void *data)
+{
+    if (env == current_env) {
+        func(data);
+        return;
+    }
+    assert(1);
+}
 
 int kvm_init_vcpu(CPUState *env)
 {
@@ -578,6 +588,7 @@ int kvm_cpu_exec(CPUState *env)
     int ret;
 
     dprintf("kvm_cpu_exec()\n");
+    current_env = env;
 
     do {
         if (env->exit_request) {
@@ -902,18 +913,32 @@ int kvm_sw_breakpoints_active(CPUState *env)
     return !TAILQ_EMPTY(&env->kvm_state->kvm_sw_breakpoints);
 }
 
+struct kvm_set_guest_debug_data {
+    struct kvm_guest_debug dbg;
+    CPUState *env;
+    int err;
+};
+
+static void kvm_invoke_set_guest_debug(void *data)
+{
+    struct kvm_set_guest_debug_data *dbg_data = data;
+    dbg_data->err = kvm_vcpu_ioctl(dbg_data->env, KVM_SET_GUEST_DEBUG, &dbg_data->dbg);
+}
+
 int kvm_update_guest_debug(CPUState *env, unsigned long reinject_trap)
 {
-    struct kvm_guest_debug dbg;
+    struct kvm_set_guest_debug_data data;
 
-    dbg.control = 0;
+    data.dbg.control = 0;
     if (env->singlestep_enabled)
-        dbg.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
+        data.dbg.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
 
-    kvm_arch_update_guest_debug(env, &dbg);
-    dbg.control |= reinject_trap;
+    kvm_arch_update_guest_debug(env, &data.dbg);
+    data.dbg.control |= reinject_trap;
+    data.env = env;
 
-    return kvm_vcpu_ioctl(env, KVM_SET_GUEST_DEBUG, &dbg);
+    on_vcpu(env, kvm_invoke_set_guest_debug, &data);
+    return data.err;
 }
 
 int kvm_insert_breakpoint(CPUState *current_env, target_ulong addr,
-- 
1.6.2.2