[PATCH v7 10/18] accel/tcg: Remove PageDesc code_bitmap

From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: alex.bennee@linaro.org
Subject: [PATCH v7 10/18] accel/tcg: Remove PageDesc code_bitmap
Date: Tue,  4 Oct 2022 07:10:43 -0700	[thread overview]
Message-ID: <20221004141051.110653-11-richard.henderson@linaro.org> (raw)
In-Reply-To: <20221004141051.110653-1-richard.henderson@linaro.org>

This bitmap is created and discarded immediately.
We gain nothing by its existence.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220822232338.1727934-2-richard.henderson@linaro.org>
---
 accel/tcg/translate-all.c | 78 ++-------------------------------------
 1 file changed, 4 insertions(+), 74 deletions(-)

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index d71d04d338..59432dc558 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -102,21 +102,14 @@
 #define assert_memory_lock() tcg_debug_assert(have_mmap_lock())
 #endif
 
-#define SMC_BITMAP_USE_THRESHOLD 10
-
 typedef struct PageDesc {
     /* list of TBs intersecting this ram page */
     uintptr_t first_tb;
-#ifdef CONFIG_SOFTMMU
-    /* in order to optimize self modifying code, we count the number
-       of lookups we do to a given page to use a bitmap */
-    unsigned long *code_bitmap;
-    unsigned int code_write_count;
-#else
+#ifdef CONFIG_USER_ONLY
     unsigned long flags;
     void *target_data;
 #endif
-#ifndef CONFIG_USER_ONLY
+#ifdef CONFIG_SOFTMMU
     QemuSpin lock;
 #endif
 } PageDesc;
@@ -907,17 +900,6 @@ void tb_htable_init(void)
     qht_init(&tb_ctx.htable, tb_cmp, CODE_GEN_HTABLE_SIZE, mode);
 }
 
-/* call with @p->lock held */
-static inline void invalidate_page_bitmap(PageDesc *p)
-{
-    assert_page_locked(p);
-#ifdef CONFIG_SOFTMMU
-    g_free(p->code_bitmap);
-    p->code_bitmap = NULL;
-    p->code_write_count = 0;
-#endif
-}
-
 /* Set to NULL all the 'first_tb' fields in all PageDescs. */
 static void page_flush_tb_1(int level, void **lp)
 {
@@ -932,7 +914,6 @@ static void page_flush_tb_1(int level, void **lp)
         for (i = 0; i < V_L2_SIZE; ++i) {
             page_lock(&pd[i]);
             pd[i].first_tb = (uintptr_t)NULL;
-            invalidate_page_bitmap(pd + i);
             page_unlock(&pd[i]);
         }
     } else {
@@ -1197,11 +1178,9 @@ static void do_tb_phys_invalidate(TranslationBlock *tb, bool rm_from_page_list)
     if (rm_from_page_list) {
         p = page_find(tb->page_addr[0] >> TARGET_PAGE_BITS);
         tb_page_remove(p, tb);
-        invalidate_page_bitmap(p);
         if (tb->page_addr[1] != -1) {
             p = page_find(tb->page_addr[1] >> TARGET_PAGE_BITS);
             tb_page_remove(p, tb);
-            invalidate_page_bitmap(p);
         }
     }
 
@@ -1246,35 +1225,6 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
     }
 }
 
-#ifdef CONFIG_SOFTMMU
-/* call with @p->lock held */
-static void build_page_bitmap(PageDesc *p)
-{
-    int n, tb_start, tb_end;
-    TranslationBlock *tb;
-
-    assert_page_locked(p);
-    p->code_bitmap = bitmap_new(TARGET_PAGE_SIZE);
-
-    PAGE_FOR_EACH_TB(p, tb, n) {
-        /* NOTE: this is subtle as a TB may span two physical pages */
-        if (n == 0) {
-            /* NOTE: tb_end may be after the end of the page, but
-               it is not a problem */
-            tb_start = tb->pc & ~TARGET_PAGE_MASK;
-            tb_end = tb_start + tb->size;
-            if (tb_end > TARGET_PAGE_SIZE) {
-                tb_end = TARGET_PAGE_SIZE;
-             }
-        } else {
-            tb_start = 0;
-            tb_end = ((tb->pc + tb->size) & ~TARGET_PAGE_MASK);
-        }
-        bitmap_set(p->code_bitmap, tb_start, tb_end - tb_start);
-    }
-}
-#endif
-
 /* add the tb in the target page and protect it if necessary
  *
  * Called with mmap_lock held for user-mode emulation.
@@ -1295,7 +1245,6 @@ static inline void tb_page_add(PageDesc *p, TranslationBlock *tb,
     page_already_protected = p->first_tb != (uintptr_t)NULL;
 #endif
     p->first_tb = (uintptr_t)tb | n;
-    invalidate_page_bitmap(p);
 
 #if defined(CONFIG_USER_ONLY)
     /* translator_loop() must have made all TB pages non-writable */
@@ -1357,10 +1306,8 @@ tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
     /* remove TB from the page(s) if we couldn't insert it */
     if (unlikely(existing_tb)) {
         tb_page_remove(p, tb);
-        invalidate_page_bitmap(p);
         if (p2) {
             tb_page_remove(p2, tb);
-            invalidate_page_bitmap(p2);
         }
         tb = existing_tb;
     }
@@ -1731,7 +1678,6 @@ tb_invalidate_phys_page_range__locked(struct page_collection *pages,
 #if !defined(CONFIG_USER_ONLY)
     /* if no code remaining, no need to continue to use slow writes */
     if (!p->first_tb) {
-        invalidate_page_bitmap(p);
         tlb_unprotect_code(start);
     }
 #endif
@@ -1827,24 +1773,8 @@ void tb_invalidate_phys_page_fast(struct page_collection *pages,
     }
 
     assert_page_locked(p);
-    if (!p->code_bitmap &&
-        ++p->code_write_count >= SMC_BITMAP_USE_THRESHOLD) {
-        build_page_bitmap(p);
-    }
-    if (p->code_bitmap) {
-        unsigned int nr;
-        unsigned long b;
-
-        nr = start & ~TARGET_PAGE_MASK;
-        b = p->code_bitmap[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG - 1));
-        if (b & ((1 << len) - 1)) {
-            goto do_invalidate;
-        }
-    } else {
-    do_invalidate:
-        tb_invalidate_phys_page_range__locked(pages, p, start, start + len,
-                                              retaddr);
-    }
+    tb_invalidate_phys_page_range__locked(pages, p, start, start + len,
+                                          retaddr);
 }
 #else
 /* Called with mmap_lock held. If pc is not 0 then it indicates the
-- 
2.34.1


