target/i386: do not trigger IRQ shadow for LSS

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: [email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
(cherry picked from commit e54ef98)
(back-ported to 10.0)
Signed-off-by: Michael Tokarev <[email protected]>

Author: bonzini

target/i386/tcg/emit.c.inc

@@ -352,7 +352,7 @@ 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) {
@@ -2372,7 +2372,7 @@ 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)

target/i386/tcg/translate.c

@@ -1992,25 +1992,32 @@ 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)) {
-        tcg_gen_trunc_tl_i32(s->tmp2_i32, src);
-        gen_helper_load_seg(tcg_env, tcg_constant_i32(seg_reg), s->tmp2_i32);
-        /* 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) {
+        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);
+
+        /* 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;
     }
 }