ide: fail I/O to empty disk

[qemu.git] / exec.c

diff --git a/exec.c b/exec.c
index b1d6602911c0330c3d35e6636384a87439fd8ba0..b81677ade9c7c67add6c4adbf4ceeb3d0d5ffe26 100644 (file)
--- a/exec.c
+++ b/exec.c
@@ -511,7 +511,7 @@ static void code_gen_alloc(unsigned long tb_size)
         if (code_gen_buffer_size > (512 * 1024 * 1024))
             code_gen_buffer_size = (512 * 1024 * 1024);
 #elif defined(__arm__)
-        /* Keep the buffer no bigger than 16GB to branch between blocks */
+        /* Keep the buffer no bigger than 16MB to branch between blocks */
         if (code_gen_buffer_size > 16 * 1024 * 1024)
             code_gen_buffer_size = 16 * 1024 * 1024;
 #elif defined(__s390x__)
@@ -1876,8 +1876,18 @@ static CPUTLBEntry s_cputlb_empty_entry = {
     .addend     = -1,
 };
 
-/* NOTE: if flush_global is true, also flush global entries (not
-   implemented yet) */
+/* NOTE:
+ * If flush_global is true (the usual case), flush all tlb entries.
+ * If flush_global is false, flush (at least) all tlb entries not
+ * marked global.
+ *
+ * Since QEMU doesn't currently implement a global/not-global flag
+ * for tlb entries, at the moment tlb_flush() will also flush all
+ * tlb entries in the flush_global == false case. This is OK because
+ * CPU architectures generally permit an implementation to drop
+ * entries from the TLB at any time, so flushing more entries than
+ * required is only an efficiency issue, not a correctness issue.
+ */
 void tlb_flush(CPUState *env, int flush_global)
 {
     int i;
@@ -4390,6 +4400,20 @@ tb_page_addr_t get_page_addr_code(CPUState *env1, target_ulong addr)
     return qemu_ram_addr_from_host_nofail(p);
 }
 
+/*
+ * A helper function for the _utterly broken_ virtio device model to find out if
+ * it's running on a big endian machine. Don't do this at home kids!
+ */
+bool virtio_is_big_endian(void);
+bool virtio_is_big_endian(void)
+{
+#if defined(TARGET_WORDS_BIGENDIAN)
+    return true;
+#else
+    return false;
+#endif
+}
+
 #define MMUSUFFIX _cmmu
 #undef GETPC
 #define GETPC() NULL