[Qemu-devel] [RFC v3 16/19] tcg: move locking for tb_invalidate_phys_page_range up

["Alex Bennée" <alex.bennee@linaro.org>]

While we previously assumed an existing memory lock protected the page
look up in the MTTCG SoftMMU case the memory lock is provided by the
tb_lock. As a result we push the taking of this lock up the call tree.
This requires a slightly different entry for the SoftMMU and user-mode
cases from tb_invalidate_phys_range.

This also means user-mode breakpoint insertion needs to take two locks
but it hadn't taken any previously so this is an improvement.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 exec.c          | 16 ++++++++++++++++
 translate-all.c | 37 +++++++++++++++++++++++++++++--------
 2 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/exec.c b/exec.c
index b7744b9..8bb7481 100644
--- a/exec.c
+++ b/exec.c
@@ -734,7 +734,11 @@ void cpu_exec_init(CPUState *cpu, Error **errp)
 #if defined(CONFIG_USER_ONLY)
 static void breakpoint_invalidate(CPUState *cpu, target_ulong pc)
 {
+    mmap_lock();
+    tb_lock();
     tb_invalidate_phys_page_range(pc, pc + 1, 0);
+    tb_unlock();
+    mmap_unlock();
 }
 #else
 static void breakpoint_invalidate(CPUState *cpu, target_ulong pc)
@@ -743,6 +747,7 @@ static void breakpoint_invalidate(CPUState *cpu, target_ulong pc)
     hwaddr phys = cpu_get_phys_page_attrs_debug(cpu, pc, &attrs);
     int asidx = cpu_asidx_from_attrs(cpu, attrs);
     if (phys != -1) {
+        /* Locks grabbed by tb_invalidate_phys_addr */
         tb_invalidate_phys_addr(cpu->cpu_ases[asidx].as,
                                 phys | (pc & ~TARGET_PAGE_MASK));
     }
@@ -2072,7 +2077,11 @@ MemoryRegion *qemu_ram_addr_from_host(void *ptr, ram_addr_t *ram_addr)
 static void notdirty_mem_write(void *opaque, hwaddr ram_addr,
                                uint64_t val, unsigned size)
 {
+    bool locked = false;
+
     if (!cpu_physical_memory_get_dirty_flag(ram_addr, DIRTY_MEMORY_CODE)) {
+        locked = true;
+        tb_lock();
         tb_invalidate_phys_page_fast(ram_addr, size);
     }
     switch (size) {
@@ -2088,6 +2097,11 @@ static void notdirty_mem_write(void *opaque, hwaddr ram_addr,
     default:
         abort();
     }
+
+    if (locked) {
+        tb_unlock();
+    }
+
     /* Set both VGA and migration bits for simplicity and to remove
      * the notdirty callback faster.
      */
@@ -2566,7 +2580,9 @@ static void invalidate_and_set_dirty(MemoryRegion *mr, hwaddr addr,
             cpu_physical_memory_range_includes_clean(addr, length, dirty_log_mask);
     }
     if (dirty_log_mask & (1 << DIRTY_MEMORY_CODE)) {
+        tb_lock();
         tb_invalidate_phys_range(addr, addr + length);
+        tb_unlock();
         dirty_log_mask &= ~(1 << DIRTY_MEMORY_CODE);
     }
     cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
diff --git a/translate-all.c b/translate-all.c
index 818520e..4bc5718 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -1355,12 +1355,11 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
  * access: the virtual CPU will exit the current TB if code is modified inside
  * this TB.
  *
- * Called with mmap_lock held for user-mode emulation
+ * Called with mmap_lock held for user-mode emulation, grabs tb_lock
+ * Called with tb_lock held for system-mode emulation
  */
-void tb_invalidate_phys_range(tb_page_addr_t start, tb_page_addr_t end)
+static void tb_invalidate_phys_range_1(tb_page_addr_t start, tb_page_addr_t end)
 {
-    assert_memory_lock();
-
     while (start < end) {
         tb_invalidate_phys_page_range(start, end, 0);
         start &= TARGET_PAGE_MASK;
@@ -1368,6 +1367,21 @@ void tb_invalidate_phys_range(tb_page_addr_t start, tb_page_addr_t end)
     }
 }
 
+#ifdef CONFIG_SOFTMMU
+void tb_invalidate_phys_range(tb_page_addr_t start, tb_page_addr_t end)
+{
+    assert_tb_lock();
+    tb_invalidate_phys_range_1(start, end);
+}
+#else
+void tb_invalidate_phys_range(tb_page_addr_t start, tb_page_addr_t end)
+{
+    assert_memory_lock();
+    tb_lock();
+    tb_invalidate_phys_range_1(start, end);
+    tb_unlock();
+}
+#endif
 /*
  * Invalidate all TBs which intersect with the target physical address range
  * [start;end[. NOTE: start and end must refer to the *same* physical page.
@@ -1375,7 +1389,8 @@ void tb_invalidate_phys_range(tb_page_addr_t start, tb_page_addr_t end)
  * access: the virtual CPU will exit the current TB if code is modified inside
  * this TB.
  *
- * Called with mmap_lock held for user-mode emulation
+ * Called with tb_lock/mmap_lock held for user-mode emulation
+ * Called with tb_lock held for system-mode emulation
  */
 void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
                                    int is_cpu_write_access)
@@ -1398,6 +1413,7 @@ void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
 #endif /* TARGET_HAS_PRECISE_SMC */
 
     assert_memory_lock();
+    assert_tb_lock();
 
     p = page_find(start >> TARGET_PAGE_BITS);
     if (!p) {
@@ -1412,7 +1428,6 @@ void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
     /* we remove all the TBs in the range [start, end[ */
     /* XXX: see if in some cases it could be faster to invalidate all
        the code */
-    tb_lock();
     tb = p->first_tb;
     while (tb != NULL) {
         n = (uintptr_t)tb & 3;
@@ -1472,12 +1487,12 @@ void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
         cpu_resume_from_signal(cpu, NULL);
     }
 #endif
-    tb_unlock();
 }
 
 #ifdef CONFIG_SOFTMMU
 /* len must be <= 8 and start must be a multiple of len.
- * Called via softmmu_template.h, with iothread mutex not held.
+ * Called via softmmu_template.h when code areas are written to with
+ * tb_lock held.
  */
 void tb_invalidate_phys_page_fast(tb_page_addr_t start, int len)
 {
@@ -1492,6 +1507,8 @@ void tb_invalidate_phys_page_fast(tb_page_addr_t start, int len)
                   (intptr_t)cpu_single_env->segs[R_CS].base);
     }
 #endif
+    assert_memory_lock();
+
     p = page_find(start >> TARGET_PAGE_BITS);
     if (!p) {
         return;
@@ -1536,6 +1553,8 @@ static void tb_invalidate_phys_page(tb_page_addr_t addr,
     uint32_t current_flags = 0;
 #endif
 
+    assert_memory_lock();
+
     addr &= TARGET_PAGE_MASK;
     p = page_find(addr >> TARGET_PAGE_BITS);
     if (!p) {
@@ -1641,7 +1660,9 @@ void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr)
         return;
     }
     ram_addr = memory_region_get_ram_addr(mr) + addr;
+    tb_lock();
     tb_invalidate_phys_page_range(ram_addr, ram_addr + 1, 0);
+    tb_unlock();
     rcu_read_unlock();
 }
 #endif /* !defined(CONFIG_USER_ONLY) */
-- 
2.7.4