[Qemu-devel] [PATCH 01/10] target/ppc: Fix nip on power management instructions

["Cédric Le Goater" <clg@kaod.org>]

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Those instructions currently raise an exception from within
the helper. This tends to result in a bogus nip value in
the env context (typically the beginning of the TB). Such
a helper needs a gen_update_nip() first.

This fixes it with a different approach which is to throw the
exception from translate.c instead of the helper using
gen_exception_nip() which does the right thing. Exception
EXCP_HLT is also used instead of POWERPC_EXCP_STOP to effectively
exit from the CPU execution loop.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[clg : modified the commit log to comment the use of EXCP_HLT instead
       of POWERPC_EXCP_STOP]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 target/ppc/excp_helper.c |  1 -
 target/ppc/translate.c   | 12 ++++++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 751d759fcc1d..8407e0ade938 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -958,7 +958,6 @@ void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t insn)
      * but this doesn't seem to be a problem.
      */
     env->msr |= (1ull << MSR_EE);
-    raise_exception(env, EXCP_HLT);
 }
 #endif /* defined(TARGET_PPC64) */
 
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index d5f29d3536e1..e94422f7ff1c 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -3565,7 +3565,8 @@ static void gen_doze(DisasContext *ctx)
     t = tcg_const_i32(PPC_PM_DOZE);
     gen_helper_pminsn(cpu_env, t);
     tcg_temp_free_i32(t);
-    gen_stop_exception(ctx);
+    /* Stop translation, as the CPU is supposed to sleep from now */
+    gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
 #endif /* defined(CONFIG_USER_ONLY) */
 }
 
@@ -3580,7 +3581,8 @@ static void gen_nap(DisasContext *ctx)
     t = tcg_const_i32(PPC_PM_NAP);
     gen_helper_pminsn(cpu_env, t);
     tcg_temp_free_i32(t);
-    gen_stop_exception(ctx);
+    /* Stop translation, as the CPU is supposed to sleep from now */
+    gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
 #endif /* defined(CONFIG_USER_ONLY) */
 }
 
@@ -3600,7 +3602,8 @@ static void gen_sleep(DisasContext *ctx)
     t = tcg_const_i32(PPC_PM_SLEEP);
     gen_helper_pminsn(cpu_env, t);
     tcg_temp_free_i32(t);
-    gen_stop_exception(ctx);
+    /* Stop translation, as the CPU is supposed to sleep from now */
+    gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
 #endif /* defined(CONFIG_USER_ONLY) */
 }
 
@@ -3615,7 +3618,8 @@ static void gen_rvwinkle(DisasContext *ctx)
     t = tcg_const_i32(PPC_PM_RVWINKLE);
     gen_helper_pminsn(cpu_env, t);
     tcg_temp_free_i32(t);
-    gen_stop_exception(ctx);
+    /* Stop translation, as the CPU is supposed to sleep from now */
+    gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next);
 #endif /* defined(CONFIG_USER_ONLY) */
 }
 #endif /* #if defined(TARGET_PPC64) */
-- 
2.20.1