[PULL 18/23] accel/tcg: re-factor non-RAM execution code

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

There is no real need to use CF_NOCACHE here. As long as the TB isn't
linked to other TBs or included in the QHT or jump cache then it will
only get executed once.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210213130325.14781-19-alex.bennee@linaro.org>

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index c0b98e76b9..72b3c663c5 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1779,7 +1779,8 @@ static inline void tb_page_add(PageDesc *p, TranslationBlock *tb,
 #endif
 }
 
-/* add a new TB and link it to the physical page tables. phys_page2 is
+/*
+ * Add a new TB and link it to the physical page tables. phys_page2 is
  * (-1) to indicate that only one page contains the TB.
  *
  * Called with mmap_lock held for user-mode emulation.
@@ -1798,17 +1799,6 @@ tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
 
     assert_memory_lock();
 
-    if (phys_pc == -1) {
-        /*
-         * If the TB is not associated with a physical RAM page then
-         * it must be a temporary one-insn TB, and we have nothing to do
-         * except fill in the page_addr[] fields.
-         */
-        assert(tb->cflags & CF_NOCACHE);
-        tb->page_addr[0] = tb->page_addr[1] = -1;
-        return tb;
-    }
-
     /*
      * Add the TB to the page list, acquiring first the pages's locks.
      * We keep the locks held until after inserting the TB in the hash table,
@@ -1881,9 +1871,8 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
     phys_pc = get_page_addr_code(env, pc);
 
     if (phys_pc == -1) {
-        /* Generate a temporary TB with 1 insn in it */
-        cflags &= ~CF_COUNT_MASK;
-        cflags |= CF_NOCACHE | 1;
+        /* Generate a one-shot TB with 1 insn in it */
+        cflags = (cflags & ~CF_COUNT_MASK) | 1;
     }
 
     cflags &= ~CF_CLUSTER_MASK;
@@ -2097,6 +2086,17 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
         tb_reset_jump(tb, 1);
     }
 
+    /*
+     * If the TB is not associated with a physical RAM page then
+     * it must be a temporary one-insn TB, and we have nothing to do
+     * except fill in the page_addr[] fields. Return early before
+     * attempting to link to other TBs or add to the lookup table.
+     */
+    if (phys_pc == -1) {
+        tb->page_addr[0] = tb->page_addr[1] = -1;
+        return tb;
+    }
+
     /* check next page if needed */
     virt_page2 = (pc + tb->size - 1) & TARGET_PAGE_MASK;
     phys_page2 = -1;
-- 
2.20.1