[Qemu-devel] [PATCH] target-i386: fix iret emulation correctness

[poletaev]

From: Dmitry Poletaev <address@hidden>

Subject: [PATCH] target-i386: fix iret emulation correctness

Signed-off-by: Dmitry Poletaev <address@hidden>

 

According to Intel manual: "If the NMI handler is a virtual-8086 task with
an IOPL of less than 3, an IRET instruction issued from the handler
generates a general-protection

exception, the NMI is unmasked before the general-protection exception
handler is invoked."

 

QEMU does not reset NMI-blocking in such situation. This patch fixes it.

---

target-i386/cc_helper.c | 5 +++++

target-i386/helper.h    | 1 +

target-i386/translate.c | 1 +

3 files changed, 7 insertions(+)

 

diff --git a/target-i386/cc_helper.c b/target-i386/cc_helper.c

index 83af223..74851ae 100644

--- a/target-i386/cc_helper.c

+++ b/target-i386/cc_helper.c

@@ -383,3 +383,8 @@ void helper_sti_vm(CPUX86State *env)

     }

}

#endif

+

+void helper_reset_nmi_blocking(CPUX86State *env)

+{

+    env->hflags2 &= ~HF2_NMI_MASK;

+}

\ No newline at end of file

diff --git a/target-i386/helper.h b/target-i386/helper.h

index 1320edc..7718d2f 100644

--- a/target-i386/helper.h

+++ b/target-i386/helper.h

@@ -70,6 +70,7 @@ DEF_HELPER_1(cli, void, env)

DEF_HELPER_1(sti, void, env)

DEF_HELPER_1(clac, void, env)

DEF_HELPER_1(stac, void, env)

+DEF_HELPER_1(reset_nmi_blocking, void, env)

DEF_HELPER_3(boundw, void, env, tl, int)

DEF_HELPER_3(boundl, void, env, tl, int)

DEF_HELPER_1(rsm, void, env)

diff --git a/target-i386/translate.c b/target-i386/translate.c

index f010022..c409baf 100644

--- a/target-i386/translate.c

+++ b/target-i386/translate.c

@@ -6319,6 +6319,7 @@ static target_ulong disas_insn(CPUX86State *env,
DisasContext *s,

             set_cc_op(s, CC_OP_EFLAGS);

         } else if (s->vm86) {

             if (s->iopl != 3) {

+                gen_helper_reset_nmi_blocking(cpu_env);

                 gen_exception(s, EXCP0D_GPF, pc_start - s->cs_base);

             } else {

                 gen_helper_iret_real(cpu_env, tcg_const_i32(dflag - 1));

-- 

1.8.4.msysgit.0

 

 

Best regards, 

Dmitry Poletaev.