tcg: tb_lock removal redux v1

[Qemu-devel] [PATCH 11/16] translate-all: add page_collection assertions

Posted by Emilio G. Cota 7 years, 7 months ago

The appended adds assertions to make sure we do not longjmp with page
locks held. Some notes:

- user-mode has nothing to check, since page_locks are !user-mode only.

- The checks only apply to page collections, since these have relatively
  complex callers.

- Some simple page_lock/unlock callers have been left unchecked --
  namely page_lock_tb, tb_phys_invalidate and tb_link_page.

Signed-off-by: Emilio G. Cota <cota@braap.org>
---
 accel/tcg/cpu-exec.c      |  1 +
 accel/tcg/translate-all.c | 22 ++++++++++++++++++++++
 include/exec/exec-all.h   |  8 ++++++++
 3 files changed, 31 insertions(+)

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 8c68727..7c83887 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -271,6 +271,7 @@ void cpu_exec_step_atomic(CPUState *cpu)
         tcg_debug_assert(!have_mmap_lock());
 #endif
         tb_lock_reset();
+        assert_page_collection_locked(false);
     }
 
     if (in_exclusive_region) {
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 07527d5..82832ef 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -605,6 +605,24 @@ void page_collection_unlock(struct page_collection *set)
 { }
 #else /* !CONFIG_USER_ONLY */
 
+#ifdef CONFIG_DEBUG_TCG
+static __thread bool page_collection_locked;
+
+void assert_page_collection_locked(bool val)
+{
+    tcg_debug_assert(page_collection_locked == val);
+}
+
+static inline void set_page_collection_locked(bool val)
+{
+    page_collection_locked = val;
+}
+#else
+static inline void set_page_collection_locked(bool val)
+{
+}
+#endif /* !CONFIG_DEBUG_TCG */
+
 static inline void page_lock(PageDesc *pd)
 {
     qemu_spin_lock(&pd->lock);
@@ -677,6 +695,7 @@ static void do_page_entry_lock(struct page_entry *pe)
     page_lock(pe->pd);
     g_assert(!pe->locked);
     pe->locked = true;
+    set_page_collection_locked(true);
 }
 
 static gboolean page_entry_lock(gpointer key, gpointer value, gpointer data)
@@ -769,6 +788,7 @@ page_collection_lock(tb_page_addr_t start, tb_page_addr_t end)
     set->tree = g_tree_new_full(tb_page_addr_cmp, NULL, NULL,
                                 page_entry_destroy);
     set->max = NULL;
+    assert_page_collection_locked(false);
 
  retry:
     g_tree_foreach(set->tree, page_entry_lock, NULL);
@@ -787,6 +807,7 @@ page_collection_lock(tb_page_addr_t start, tb_page_addr_t end)
                  page_trylock_add(set, tb->page_addr[1]))) {
                 /* drop all locks, and reacquire in order */
                 g_tree_foreach(set->tree, page_entry_unlock, NULL);
+                set_page_collection_locked(false);
                 goto retry;
             }
         }
@@ -799,6 +820,7 @@ void page_collection_unlock(struct page_collection *set)
     /* entries are unlocked and freed via page_entry_destroy */
     g_tree_destroy(set->tree);
     g_free(set);
+    set_page_collection_locked(false);
 }
 
 #endif /* !CONFIG_USER_ONLY */
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index aeaa127..7911e69 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -431,6 +431,14 @@ void tb_lock(void);
 void tb_unlock(void);
 void tb_lock_reset(void);
 
+#if !defined(CONFIG_USER_ONLY) && defined(CONFIG_DEBUG_TCG)
+void assert_page_collection_locked(bool val);
+#else
+static inline void assert_page_collection_locked(bool val)
+{
+}
+#endif
+
 #if !defined(CONFIG_USER_ONLY)
 
 struct MemoryRegion *iotlb_to_region(CPUState *cpu,
-- 
2.7.4

Re: [Qemu-devel] [PATCH 11/16] translate-all: add page_collection assertions

Posted by Alex Bennée 7 years, 6 months ago

Emilio G. Cota <cota@braap.org> writes:

> The appended adds assertions to make sure we do not longjmp with page
> locks held. Some notes:
>
> - user-mode has nothing to check, since page_locks are !user-mode only.
>
> - The checks only apply to page collections, since these have relatively
>   complex callers.
>
> - Some simple page_lock/unlock callers have been left unchecked --
>   namely page_lock_tb, tb_phys_invalidate and tb_link_page.

As mentioned in the previous email I think there is a need for
assert_page_locked() at least for places currently still using
assert_memory_locked(). It could certainly be DEBUG_TCG only case
though.

Otherwise:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> ---
>  accel/tcg/cpu-exec.c      |  1 +
>  accel/tcg/translate-all.c | 22 ++++++++++++++++++++++
>  include/exec/exec-all.h   |  8 ++++++++
>  3 files changed, 31 insertions(+)
>
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 8c68727..7c83887 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -271,6 +271,7 @@ void cpu_exec_step_atomic(CPUState *cpu)
>          tcg_debug_assert(!have_mmap_lock());
>  #endif
>          tb_lock_reset();
> +        assert_page_collection_locked(false);
>      }
>
>      if (in_exclusive_region) {
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index 07527d5..82832ef 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -605,6 +605,24 @@ void page_collection_unlock(struct page_collection *set)
>  { }
>  #else /* !CONFIG_USER_ONLY */
>
> +#ifdef CONFIG_DEBUG_TCG
> +static __thread bool page_collection_locked;
> +
> +void assert_page_collection_locked(bool val)
> +{
> +    tcg_debug_assert(page_collection_locked == val);
> +}
> +
> +static inline void set_page_collection_locked(bool val)
> +{
> +    page_collection_locked = val;
> +}
> +#else
> +static inline void set_page_collection_locked(bool val)
> +{
> +}
> +#endif /* !CONFIG_DEBUG_TCG */
> +
>  static inline void page_lock(PageDesc *pd)
>  {
>      qemu_spin_lock(&pd->lock);
> @@ -677,6 +695,7 @@ static void do_page_entry_lock(struct page_entry *pe)
>      page_lock(pe->pd);
>      g_assert(!pe->locked);
>      pe->locked = true;
> +    set_page_collection_locked(true);
>  }
>
>  static gboolean page_entry_lock(gpointer key, gpointer value, gpointer data)
> @@ -769,6 +788,7 @@ page_collection_lock(tb_page_addr_t start, tb_page_addr_t end)
>      set->tree = g_tree_new_full(tb_page_addr_cmp, NULL, NULL,
>                                  page_entry_destroy);
>      set->max = NULL;
> +    assert_page_collection_locked(false);
>
>   retry:
>      g_tree_foreach(set->tree, page_entry_lock, NULL);
> @@ -787,6 +807,7 @@ page_collection_lock(tb_page_addr_t start, tb_page_addr_t end)
>                   page_trylock_add(set, tb->page_addr[1]))) {
>                  /* drop all locks, and reacquire in order */
>                  g_tree_foreach(set->tree, page_entry_unlock, NULL);
> +                set_page_collection_locked(false);
>                  goto retry;
>              }
>          }
> @@ -799,6 +820,7 @@ void page_collection_unlock(struct page_collection *set)
>      /* entries are unlocked and freed via page_entry_destroy */
>      g_tree_destroy(set->tree);
>      g_free(set);
> +    set_page_collection_locked(false);
>  }
>
>  #endif /* !CONFIG_USER_ONLY */
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index aeaa127..7911e69 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -431,6 +431,14 @@ void tb_lock(void);
>  void tb_unlock(void);
>  void tb_lock_reset(void);
>
> +#if !defined(CONFIG_USER_ONLY) && defined(CONFIG_DEBUG_TCG)
> +void assert_page_collection_locked(bool val);
> +#else
> +static inline void assert_page_collection_locked(bool val)
> +{
> +}
> +#endif
> +
>  #if !defined(CONFIG_USER_ONLY)
>
>  struct MemoryRegion *iotlb_to_region(CPUState *cpu,


--
Alex Bennée