[Qemu-devel] [RFC PATCH v6 10/32] 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       |    3 +++
 target-i386/translate.c |   14 ++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 015f5b5..ca94f8f 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -28,6 +28,9 @@
 #define TARGET_LONG_BITS 32
 #endif
 
+/* Maximum instruction code size */
+#define TARGET_MAX_INSN_SIZE 16
+
 /* 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 6243e36..fc75da7 100644
--- a/target-i386/translate.c
+++ b/target-i386/translate.c
@@ -8034,6 +8034,20 @@ 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) ||