[Qemu-devel] [PATCHv2 23/31] ppc: Make alignment exceptions suck less

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: qemu-ppc@nongnu.org
Cc: qemu-devel@nongnu.org, david@gibson.dropbear.id.au,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: [Qemu-devel] [PATCHv2 23/31] ppc: Make alignment exceptions suck less
Date: Wed, 27 Jul 2016 16:56:41 +1000	[thread overview]
Message-ID: <1469602609-31349-23-git-send-email-benh@kernel.crashing.org> (raw)
In-Reply-To: <1469602609-31349-1-git-send-email-benh@kernel.crashing.org>

The current alignment exception generation tries to load the opcode
to put in DSISR from a context where a cpu_ldl_code() is really not
a good idea. It might fault and longjmp out and that's not something
we want happening here.

Instead, pass the releavant opcode bits via the error_code.

There are a couple of cases of alignment interrupts that won't set
anything, the ones coming from access to direct store segments, but
that doesn't happen in practice, nobody used direct store segments
and they are gone from newer chips.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
 target-ppc/excp_helper.c | 9 +++++----
 target-ppc/translate.c   | 2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/target-ppc/excp_helper.c b/target-ppc/excp_helper.c
index 882d529..04ed4da 100644
--- a/target-ppc/excp_helper.c
+++ b/target-ppc/excp_helper.c
@@ -260,11 +260,12 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int excp_model, int excp)
         }
         break;
     case POWERPC_EXCP_ALIGN:     /* Alignment exception                      */
-        /* XXX: this is false */
         /* Get rS/rD and rA from faulting opcode */
-        /* Broken for LE mode */
-        env->spr[SPR_DSISR] |= (cpu_ldl_code(env, env->nip)
-                                & 0x03FF0000) >> 16;
+        /* Note: the opcode fields will not be set properly for a direct
+         * store load/store, but nobody cares as nobody actually uses
+         * direct store segments.
+         */
+        env->spr[SPR_DSISR] |= (env->error_code & 0x03FF0000) >> 16;
         break;
     case POWERPC_EXCP_PROGRAM:   /* Program exception                        */
         switch (env->error_code & ~0xF) {
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index 5c68b1d..20c9cbb 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -2416,7 +2416,7 @@ static inline void gen_check_align(DisasContext *ctx, TCGv EA, int mask)
     tcg_gen_andi_tl(t0, EA, mask);
     tcg_gen_brcondi_tl(TCG_COND_EQ, t0, 0, l1);
     t1 = tcg_const_i32(POWERPC_EXCP_ALIGN);
-    t2 = tcg_const_i32(0);
+    t2 = tcg_const_i32(ctx->opcode & 0x03FF0000);
     gen_update_nip(ctx, ctx->nip - 4);
     gen_helper_raise_exception_err(cpu_env, t1, t2);
     tcg_temp_free_i32(t1);
-- 
2.7.4
