[PATCH 09/11] target/i386: fix TF/RF handling for HLT

[Paolo Bonzini]

HLT uses DISAS_NORETURN because the corresponding helper calls
cpu_loop_exit().  However, while gen_eob() clears HF_RF_MASK and
synthesizes a #DB exception if single-step is active, none of this is
done by HLT.  Note that the single-step trap is generated after the halt
is finished.

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 target/i386/tcg/sysemu/misc_helper.c |  2 +-
 target/i386/tcg/sysemu/seg_helper.c  | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/target/i386/tcg/sysemu/misc_helper.c 
b/target/i386/tcg/sysemu/misc_helper.c
index 093cc2d0f90..7fa0c5a06de 100644
--- a/target/i386/tcg/sysemu/misc_helper.c
+++ b/target/i386/tcg/sysemu/misc_helper.c
@@ -520,7 +520,7 @@ G_NORETURN void helper_hlt(CPUX86State *env)
 {
     CPUState *cs = env_cpu(env);
 
-    env->hflags &= ~HF_INHIBIT_IRQ_MASK; /* needed if sti is just before */
+    do_end_instruction(env);
     cs->halted = 1;
     cs->exception_index = EXCP_HLT;
     cpu_loop_exit(cs);
diff --git a/target/i386/tcg/sysemu/seg_helper.c 
b/target/i386/tcg/sysemu/seg_helper.c
index 9ba94deb3aa..05174a79e73 100644
--- a/target/i386/tcg/sysemu/seg_helper.c
+++ b/target/i386/tcg/sysemu/seg_helper.c
@@ -130,15 +130,26 @@ void x86_cpu_do_interrupt(CPUState *cs)
 
 bool x86_cpu_exec_halt(CPUState *cpu)
 {
-    if (cpu->interrupt_request & CPU_INTERRUPT_POLL) {
-        X86CPU *x86_cpu = X86_CPU(cpu);
+    X86CPU *x86_cpu = X86_CPU(cpu);
+    CPUX86State *env = &x86_cpu->env;
 
+    if (cpu->interrupt_request & CPU_INTERRUPT_POLL) {
         bql_lock();
         apic_poll_irq(x86_cpu->apic_state);
         cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
         bql_unlock();
     }
-    return cpu_has_work(cpu);
+
+    if (!cpu_has_work(cpu)) {
+        return false;
+    }
+
+    /* Complete HLT instruction.  */
+    if (env->eflags & TF_MASK) {
+        env->dr[6] |= DR6_BS;
+        do_interrupt_all(x86_cpu, EXCP01_DB, 0, 0, env->eip, 0);
+    }
+    return true;
 }
 
 bool x86_need_replay_interrupt(int interrupt_request)
-- 
2.45.1