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Re: [PATCH] bsd-user/main: Allow setting tb-size


From: Warner Losh
Subject: Re: [PATCH] bsd-user/main: Allow setting tb-size
Date: Wed, 31 Jul 2024 15:21:44 -0600

On Wed, Jul 31, 2024 at 8:45 AM Ilya Leoshkevich <iii@linux.ibm.com> wrote:
While qemu-system can set tb-size using -accel tcg,tb-size=n, there
is no similar knob for qemu-bsd-user. Add one in a way similar to how
one-insn-per-tb is already handled.

Cool! Are you using bsd-user and need this for some reason? Or is this
purely theoretical? Is there a larger context I can read about somewhere?

I'll merge it either way (so none of the above is a criticism, I'm genuinely
curious) , but I don't get too many bsd-user fixes and this one is unusual.
 
Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 bsd-user/main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/bsd-user/main.c b/bsd-user/main.c
index cc980e6f401..7c230b0c7a5 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -60,6 +60,7 @@ uintptr_t qemu_host_page_size;
 intptr_t qemu_host_page_mask;

 static bool opt_one_insn_per_tb;
+static unsigned long opt_tb_size;
 uintptr_t guest_base;
 bool have_guest_base;
 /*
@@ -169,6 +170,7 @@ static void usage(void)
            "                  (use '-d help' for a list of log items)\n"
            "-D logfile        write logs to 'logfile' (default stderr)\n"
            "-one-insn-per-tb  run with one guest instruction per emulated TB\n"
+           "-tb-size size     TCG translation block cache size\n"
            "-strace           log system calls\n"
            "-trace            [[enable=]<pattern>][,events=<file>][,file=<file>]\n"
            "                  specify tracing options\n"
@@ -387,6 +389,11 @@ int main(int argc, char **argv)
             seed_optarg = optarg;
         } else if (!strcmp(r, "one-insn-per-tb")) {
             opt_one_insn_per_tb = true;
+        } else if (!strcmp(r, "tb-size")) {
+            r = argv[optind++];
+            if (qemu_strtoul(r, NULL, 0, &opt_tb_size)) {
+                usage();
+            }
         } else if (!strcmp(r, "strace")) {
             do_strace = 1;
         } else if (!strcmp(r, "trace")) {
@@ -452,6 +459,8 @@ int main(int argc, char **argv)
         accel_init_interfaces(ac);
         object_property_set_bool(OBJECT(accel), "one-insn-per-tb",
                                  opt_one_insn_per_tb, &error_abort);
+        object_property_set_int(OBJECT(accel), "tb-size",
+                                opt_tb_size, &error_abort);
         ac->init_machine(NULL);
     }

Reviewed-by: Warner Losh <imp@bsdimp.com>

I'll queue this to my bsd-user-2024-q3-2 branch. I hope to land it, just after 9.1.0 release.

Warner

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