[Qemu-devel] [RFC PATCH v4 10/25] i386: do not cross the pages boundaries in replay mode

[Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>]

This patch denies crossing the boundary of the pages in the replay mode,
because it can cause an exception. Do it only when boundary is
crossed by the first instruction in the block.
If current instruction already crossed the bound - it's ok,
because an exception hasn't stopped this code.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
---
 target-i386/cpu.h       |    7 +++++++
 target-i386/translate.c |   14 ++++++++++++++
 2 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 2968749..bc3f9f5 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -28,6 +28,13 @@
 #define TARGET_LONG_BITS 32
 #endif
 
+/* Maximum instruction code size */
+#ifdef TARGET_X86_64
+#define TARGET_MAX_INSN_SIZE 16
+#else
+#define TARGET_MAX_INSN_SIZE 16
+#endif
+
 /* target supports implicit self modifying code */
 #define TARGET_HAS_SMC
 /* support for self modifying code even if the modified instruction is
diff --git a/target-i386/translate.c b/target-i386/translate.c
index 4d5dfb3..a264908 100644
--- a/target-i386/translate.c
+++ b/target-i386/translate.c
@@ -8035,6 +8035,20 @@ static inline void gen_intermediate_code_internal(X86CPU *cpu,
             gen_eob(dc);
             break;
         }
+        /* Do not cross the boundary of the pages in icount mode,
+           it can cause an exception. Do it only when boundary is
+           crossed by the first instruction in the block.
+           If current instruction already crossed the bound - it's ok,
+           because an exception hasn't stopped this code.
+         */
+        if (use_icount
+            && ((pc_ptr & TARGET_PAGE_MASK)
+                != ((pc_ptr + TARGET_MAX_INSN_SIZE - 1) & TARGET_PAGE_MASK)
+                || (pc_ptr & ~TARGET_PAGE_MASK) == 0)) {
+            gen_jmp_im(pc_ptr - dc->cs_base);
+            gen_eob(dc);
+            break;
+        }
         /* if too long translation, stop generation too */
         if (tcg_ctx.gen_opc_ptr >= gen_opc_end ||
             (pc_ptr - pc_start) >= (TARGET_PAGE_SIZE - 32) ||