[RFC PATCH 2/5] linux-user: Add '-one-insn-per-tb' option equivalent to '-singlestep'

[Peter Maydell <peter.maydell@linaro.org>]

The '-singlestep' option is confusing, because it doesn't actually
have anything to do with single-stepping the CPU. What it does do
is force TCG emulation to put one guest instruction in each TB,
which can be useful in some situations.

Create a new command line argument -one-insn-per-tb, so we can
document that -singlestep is just a deprecated synonym for it,
and eventually perhaps drop it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 docs/user/main.rst | 7 ++++++-
 linux-user/main.c  | 9 ++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/docs/user/main.rst b/docs/user/main.rst
index 6f2ffa080f7..f9ac701f4b1 100644
--- a/docs/user/main.rst
+++ b/docs/user/main.rst
@@ -93,8 +93,13 @@ Debug options:
 ``-g port``
    Wait gdb connection to port
 
+``-one-insn-per-tb``
+   Run the emulation with one guest instruction per translation block.
+   This slows down emulation a lot, but can be useful in some situations,
+   such as when trying to analyse the logs produced by the ``-d`` option.
+
 ``-singlestep``
-   Run the emulation in single step mode.
+   This is a deprecated synonym for the ``-one-insn-per-tb`` option.
 
 Environment variables:
 
diff --git a/linux-user/main.c b/linux-user/main.c
index 99bcd542b42..41089e51cea 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -395,7 +395,7 @@ static void handle_arg_reserved_va(const char *arg)
     }
 }
 
-static void handle_arg_singlestep(const char *arg)
+static void handle_arg_one_insn_per_tb(const char *arg)
 {
     one_insn_per_tb = 1;
 }
@@ -486,8 +486,11 @@ static const struct qemu_argument arg_table[] = {
      "logfile",     "write logs to 'logfile' (default stderr)"},
     {"p",          "QEMU_PAGESIZE",    true,  handle_arg_pagesize,
      "pagesize",   "set the host page size to 'pagesize'"},
-    {"singlestep", "QEMU_SINGLESTEP",  false, handle_arg_singlestep,
-     "",           "run in singlestep mode"},
+    {"one-insn-per-tb",
+                   "QEMU_ONE_INSN_PER_TB",  false, handle_arg_one_insn_per_tb,
+     "",           "run with one guest instruction per emulated TB"},
+    {"singlestep", "QEMU_SINGLESTEP",  false, handle_arg_one_insn_per_tb,
+     "",           "deprecated synonym for -one-insn-per-tb"},
     {"strace",     "QEMU_STRACE",      false, handle_arg_strace,
      "",           "log system calls"},
     {"seed",       "QEMU_RAND_SEED",   true,  handle_arg_seed,
-- 
2.34.1