From: Gustavo Romero <gromero@linux.ibm.com>

Currently if option '-icount auto' is passed to the QEMU TCG to enable
counting instructions the VM crashes with the following error report when
Linux runs on it:

qemu-system-ppc64: Bad icount read

This happens because read/write access to the SPRs PURR, VTB, and TBU40
is not integrated to the icount framework.

This commit fixes that issue by making the read/write access of these
SPRs aware of icount framework, adding the proper gen_io_start() calls
before calling the helpers to load/store these SPRs in TCG and ensuring
that the associated TBs end immediately after, accordingly to what's in
docs/devel/tcg-icount.rst.

Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
Message-Id: <20200811153235.4527-1-gromero@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target/ppc/translate_init.inc.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/target/ppc/translate_init.inc.c b/target/ppc/translate_init.inc.c
index 5134123dd6..230a062d29 100644
--- a/target/ppc/translate_init.inc.c
+++ b/target/ppc/translate_init.inc.c
@@ -284,12 +284,24 @@ static void spr_write_atbu(DisasContext *ctx, int sprn, int gprn)
 ATTRIBUTE_UNUSED
 static void spr_read_purr(DisasContext *ctx, int gprn, int sprn)
 {
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
     gen_helper_load_purr(cpu_gpr[gprn], cpu_env);
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_stop_exception(ctx);
+    }
 }
 
 static void spr_write_purr(DisasContext *ctx, int sprn, int gprn)
 {
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
     gen_helper_store_purr(cpu_env, cpu_gpr[gprn]);
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_stop_exception(ctx);
+    }
 }
 
 /* HDECR */
@@ -319,17 +331,35 @@ static void spr_write_hdecr(DisasContext *ctx, int sprn, int gprn)
 
 static void spr_read_vtb(DisasContext *ctx, int gprn, int sprn)
 {
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
     gen_helper_load_vtb(cpu_gpr[gprn], cpu_env);
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_stop_exception(ctx);
+    }
 }
 
 static void spr_write_vtb(DisasContext *ctx, int sprn, int gprn)
 {
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
     gen_helper_store_vtb(cpu_env, cpu_gpr[gprn]);
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_stop_exception(ctx);
+    }
 }
 
 static void spr_write_tbu40(DisasContext *ctx, int sprn, int gprn)
 {
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
     gen_helper_store_tbu40(cpu_env, cpu_gpr[gprn]);
+    if (tb_cflags(ctx->base.tb) & CF_USE_ICOUNT) {
+        gen_stop_exception(ctx);
+    }
 }
 
 #endif
-- 
2.26.2