[Qemu-devel] [PATCH v7 7/7] vcpu: push mmio dispatcher out of big lock

[Liu Ping Fan <qemulist@gmail.com>]

From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>

To anti the recursive big lock, introduce separate interfaces to allow
address space dispatcher called with/without big lock.

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
 cpu-common.h |    3 +++
 exec.c       |   21 +++++++++++++++++----
 kvm-all.c    |    4 +++-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/cpu-common.h b/cpu-common.h
index c0d27af..69c1d7a 100644
--- a/cpu-common.h
+++ b/cpu-common.h
@@ -51,6 +51,9 @@ void qemu_ram_set_idstr(ram_addr_t addr, const char *name, DeviceState *dev);
 
 void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
                             int len, int is_write);
+void cpu_physical_memory_nolock_rw(target_phys_addr_t addr, uint8_t *buf,
+                            int len, int is_write);
+
 static inline void cpu_physical_memory_read(target_phys_addr_t addr,
                                             void *buf, int len)
 {
diff --git a/exec.c b/exec.c
index 7eae54e..9fec600 100644
--- a/exec.c
+++ b/exec.c
@@ -3468,8 +3468,8 @@ static void address_space_dec_req_pending(void)
     thread_context.req_pending--;
 }
 
-void address_space_rw(AddressSpace *as, target_phys_addr_t addr, uint8_t *buf,
-                      int len, bool is_write)
+static void address_space_rw_internal(AddressSpace *as, target_phys_addr_t addr,
+                      uint8_t *buf, int len, bool is_write, bool biglock)
 {
     AddressSpaceDispatch *d = as->dispatch;
     int l;
@@ -3493,7 +3493,7 @@ void address_space_rw(AddressSpace *as, target_phys_addr_t addr, uint8_t *buf,
             goto skip;
         }
 
-        if (!safe_ref) {
+        if (!safe_ref && !biglock) {
             qemu_mutex_lock_iothread();
             qemu_mutex_lock(&as->lock);
             /* when 2nd try, mem map can change, need to judge it again */
@@ -3576,12 +3576,18 @@ skip:
         len -= l;
         buf += l;
         addr += l;
-        if (!safe_ref) {
+        if (!safe_ref && !biglock) {
             qemu_mutex_unlock_iothread();
         }
     }
 }
 
+void address_space_rw(AddressSpace *as, target_phys_addr_t addr, uint8_t *buf,
+                      int len, bool is_write)
+{
+    address_space_rw_internal(as, addr, buf, len, is_write, true);
+}
+
 void address_space_write(AddressSpace *as, target_phys_addr_t addr,
                          const uint8_t *buf, int len)
 {
@@ -3607,6 +3613,13 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
     return address_space_rw(&address_space_memory, addr, buf, len, is_write);
 }
 
+void cpu_physical_memory_nolock_rw(target_phys_addr_t addr, uint8_t *buf,
+                            int len, int is_write)
+{
+    return address_space_rw_internal(&address_space_memory, addr, buf, len,
+           is_write, false);
+}
+
 /* used for ROM loading : can write in RAM and ROM */
 void cpu_physical_memory_write_rom(target_phys_addr_t addr,
                                    const uint8_t *buf, int len)
diff --git a/kvm-all.c b/kvm-all.c
index c2c6909..41261d2 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1573,10 +1573,12 @@ int kvm_cpu_exec(CPUArchState *env)
             break;
         case KVM_EXIT_MMIO:
             DPRINTF("handle_mmio\n");
-            cpu_physical_memory_rw(run->mmio.phys_addr,
+            qemu_mutex_unlock_iothread();
+            cpu_physical_memory_nolock_rw(run->mmio.phys_addr,
                                    run->mmio.data,
                                    run->mmio.len,
                                    run->mmio.is_write);
+            qemu_mutex_lock_iothread();
             ret = 0;
             break;
         case KVM_EXIT_IRQ_WINDOW_OPEN:
-- 
1.7.4.4