[PATCH 1/2] target/i386: do not trigger IRQ shadow for LSS

[Paolo Bonzini <pbonzini@redhat.com>]

Because LSS need not trigger an IRQ shadow, gen_movl_seg can't just use
the destination register to decide whether to inhibit IRQs.  Add an
argument.

Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 target/i386/tcg/translate.c | 27 ++++++++++++++++-----------
 target/i386/tcg/emit.c.inc  |  4 ++--
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index 8a641951cd1..a4e935b043b 100644
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -2026,27 +2026,32 @@ static void gen_op_movl_seg_real(DisasContext *s, X86Seg seg_reg, TCGv seg)
 
 /* move SRC to seg_reg and compute if the CPU state may change. Never
    call this function with seg_reg == R_CS */
-static void gen_movl_seg(DisasContext *s, X86Seg seg_reg, TCGv src)
+static void gen_movl_seg(DisasContext *s, X86Seg seg_reg, TCGv src, bool inhibit_irq)
 {
     if (PE(s) && !VM86(s)) {
         TCGv_i32 sel = tcg_temp_new_i32();
 
         tcg_gen_trunc_tl_i32(sel, src);
         gen_helper_load_seg(tcg_env, tcg_constant_i32(seg_reg), sel);
-        /* abort translation because the addseg value may change or
-           because ss32 may change. For R_SS, translation must always
-           stop as a special handling must be done to disable hardware
-           interrupts for the next instruction */
-        if (seg_reg == R_SS) {
-            s->base.is_jmp = DISAS_EOB_INHIBIT_IRQ;
-        } else if (CODE32(s) && seg_reg < R_FS) {
+
+        /* For move to DS/ES/SS, the addseg or ss32 flags may change.  */
+        if (CODE32(s) && seg_reg < R_FS) {
             s->base.is_jmp = DISAS_EOB_NEXT;
         }
     } else {
         gen_op_movl_seg_real(s, seg_reg, src);
-        if (seg_reg == R_SS) {
-            s->base.is_jmp = DISAS_EOB_INHIBIT_IRQ;
-        }
+    }
+
+    /*
+     * For MOV or POP to SS (but not LSS) translation must always
+     * stop as a special handling must be done to disable hardware
+     * interrupts for the next instruction.
+     *
+     * DISAS_EOB_INHIBIT_IRQ is a superset of DISAS_EOB_NEXT which
+     * might have been set above.
+     */
+    if (inhibit_irq) {
+        s->base.is_jmp = DISAS_EOB_INHIBIT_IRQ;
     }
 }
 
diff --git a/target/i386/tcg/emit.c.inc b/target/i386/tcg/emit.c.inc
index e3166e70a5b..1a7fab9333a 100644
--- a/target/i386/tcg/emit.c.inc
+++ b/target/i386/tcg/emit.c.inc
@@ -342,7 +342,7 @@ static void gen_writeback(DisasContext *s, X86DecodedInsn *decode, int opn, TCGv
         break;
     case X86_OP_SEG:
         /* Note that gen_movl_seg takes care of interrupt shadow and TF.  */
-        gen_movl_seg(s, op->n, s->T0);
+        gen_movl_seg(s, op->n, v, op->n == R_SS);
         break;
     case X86_OP_INT:
         if (op->has_ea) {
@@ -2382,7 +2382,7 @@ static void gen_lxx_seg(DisasContext *s, X86DecodedInsn *decode, int seg)
     gen_op_ld_v(s, MO_16, s->T1, s->A0);
 
     /* load the segment here to handle exceptions properly */
-    gen_movl_seg(s, seg, s->T1);
+    gen_movl_seg(s, seg, s->T1, false);
 }
 
 static void gen_LDS(DisasContext *s, X86DecodedInsn *decode)
-- 
2.49.0