tcg: Allocate code_gen_buffer into struct tcg_region_state

Do not mess around with setting values within tcg_init_ctx.
Put the values into 'region' directly, which is where they
will live for the lifetime of the program.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Luis Pires <luis.pires@eldorado.org.br>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tcg/region.c

@@ -70,13 +70,12 @@ static size_t tree_size;
 
 bool in_code_gen_buffer(const void *p)
 {
-    const TCGContext *s = &tcg_init_ctx;
     /*
      * Much like it is valid to have a pointer to the byte past the
      * end of an array (so long as you don't dereference it), allow
      * a pointer to the byte past the end of the code gen buffer.
      */
-    return (size_t)(p - s->code_gen_buffer) <= s->code_gen_buffer_size;
+    return (size_t)(p - region.start_aligned) <= region.total_size;
 }
 
 #ifdef CONFIG_DEBUG_TCG
@@ -562,8 +561,8 @@ static bool alloc_code_gen_buffer(size_t tb_size, int splitwx, Error **errp)
     }
     qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);
 
-    tcg_ctx->code_gen_buffer = buf;
-    tcg_ctx->code_gen_buffer_size = size;
+    region.start_aligned = buf;
+    region.total_size = size;
     return true;
 }
 #elif defined(_WIN32)
@@ -584,8 +583,8 @@ static bool alloc_code_gen_buffer(size_t size, int splitwx, Error **errp)
         return false;
     }
 
-    tcg_ctx->code_gen_buffer = buf;
-    tcg_ctx->code_gen_buffer_size = size;
+    region.start_aligned = buf;
+    region.total_size = size;
     return true;
 }
 #else
@@ -637,8 +636,8 @@ static bool alloc_code_gen_buffer_anon(size_t size, int prot,
     /* Request large pages for the buffer.  */
     qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);
 
-    tcg_ctx->code_gen_buffer = buf;
-    tcg_ctx->code_gen_buffer_size = size;
+    region.start_aligned = buf;
+    region.total_size = size;
     return true;
 }
 
@@ -659,8 +658,8 @@ static bool alloc_code_gen_buffer_splitwx_memfd(size_t size, Error **errp)
         return false;
     }
     /* The size of the mapping may have been adjusted. */
-    size = tcg_ctx->code_gen_buffer_size;
-    buf_rx = tcg_ctx->code_gen_buffer;
+    buf_rx = region.start_aligned;
+    size = region.total_size;
 #endif
 
     buf_rw = qemu_memfd_alloc("tcg-jit", size, 0, &fd, errp);
@@ -682,8 +681,8 @@ static bool alloc_code_gen_buffer_splitwx_memfd(size_t size, Error **errp)
 #endif
 
     close(fd);
-    tcg_ctx->code_gen_buffer = buf_rw;
-    tcg_ctx->code_gen_buffer_size = size;
+    region.start_aligned = buf_rw;
+    region.total_size = size;
     tcg_splitwx_diff = buf_rx - buf_rw;
 
     /* Request large pages for the buffer and the splitwx.  */
@@ -734,7 +733,7 @@ static bool alloc_code_gen_buffer_splitwx_vmremap(size_t size, Error **errp)
         return false;
     }
 
-    buf_rw = (mach_vm_address_t)tcg_ctx->code_gen_buffer;
+    buf_rw = (mach_vm_address_t)region.start_aligned;
     buf_rx = 0;
     ret = mach_vm_remap(mach_task_self(),
                         &buf_rx,
@@ -846,51 +845,42 @@ static bool alloc_code_gen_buffer(size_t size, int splitwx, Error **errp)
  */
 void tcg_region_init(size_t tb_size, int splitwx, unsigned max_cpus)
 {
-    void *buf, *aligned, *end;
-    size_t total_size;
     size_t page_size;
     size_t region_size;
-    size_t n_regions;
     size_t i;
     bool ok;
 
     ok = alloc_code_gen_buffer(size_code_gen_buffer(tb_size),
                                splitwx, &error_fatal);
     assert(ok);
 
-    buf = tcg_init_ctx.code_gen_buffer;
-    total_size = tcg_init_ctx.code_gen_buffer_size;
-    page_size = qemu_real_host_page_size;
-    n_regions = tcg_n_regions(total_size, max_cpus);
-
-    /* The first region will be 'aligned - buf' bytes larger than the others */
-    aligned = QEMU_ALIGN_PTR_UP(buf, page_size);
-    g_assert(aligned < tcg_init_ctx.code_gen_buffer + total_size);
-
     /*
      * Make region_size a multiple of page_size, using aligned as the start.
      * As a result of this we might end up with a few extra pages at the end of
      * the buffer; we will assign those to the last region.
      */
-    region_size = (total_size - (aligned - buf)) / n_regions;
+    region.n = tcg_n_regions(region.total_size, max_cpus);
+    page_size = qemu_real_host_page_size;
+    region_size = region.total_size / region.n;
     region_size = QEMU_ALIGN_DOWN(region_size, page_size);
 
     /* A region must have at least 2 pages; one code, one guard */
     g_assert(region_size >= 2 * page_size);
+    region.stride = region_size;
+
+    /* Reserve space for guard pages. */
+    region.size = region_size - page_size;
+    region.total_size -= page_size;
+
+    /*
+     * The first region will be smaller than the others, via the prologue,
+     * which has yet to be allocated.  For now, the first region begins at
+     * the page boundary.
+     */
+    region.after_prologue = region.start_aligned;
 
     /* init the region struct */
     qemu_mutex_init(&region.lock);
-    region.n = n_regions;
-    region.size = region_size - page_size;
-    region.stride = region_size;
-    region.after_prologue = buf;
-    region.start_aligned = aligned;
-    /* page-align the end, since its last page will be a guard page */
-    end = QEMU_ALIGN_PTR_DOWN(buf + total_size, page_size);
-    /* account for that last guard page */
-    end -= page_size;
-    total_size = end - aligned;
-    region.total_size = total_size;
 
     /*
      * Set guard pages in the rw buffer, as that's the one into which