* Steven Sistare (steven.sist...@oracle.com) wrote:
> On 7/30/2020 1:03 PM, Alex Bennée wrote:
> >
> > Steve Sistare <steven.sist...@oracle.com> writes:
> >
> >> Provide the -pause command-line parameter and the QEMU_PAUSE environment
> >> variable to briefly pause QEMU in main and allow a developer to attach gdb.
> >> Useful when the developer does not invoke QEMU directly, such as when using
> >> libvirt.
> >
> > How does this differ from -S?
>
> The -S flag runs qemu to the main loop but does not start the guest. Lots of
> code
> that you may need to debug runs before you get there.
You might try the '--preconfig' option - that's pretty early on.
The other one is adding a chardev and telling it to wait for a server;
that'll wait until you telnet to the port.
(Either way, this patch shouldn't really be part of this series, it's a
separate discussion)
Dave
> - Steve
> >> Usage:
> >> qemu -pause <seconds>
> >> or
> >> export QEMU_PAUSE=<seconds>
> >>
> >> Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
> >> ---
> >> qemu-options.hx | 9 +++++++++
> >> softmmu/vl.c | 15 ++++++++++++++-
> >> 2 files changed, 23 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/qemu-options.hx b/qemu-options.hx
> >> index 708583b..8505cf2 100644
> >> --- a/qemu-options.hx
> >> +++ b/qemu-options.hx
> >> @@ -3668,6 +3668,15 @@ SRST
> >> option is experimental.
> >> ERST
> >>
> >> +DEF("pause", HAS_ARG, QEMU_OPTION_pause, \
> >> + "-pause secs Pause for secs seconds on entry to main.\n",
> >> QEMU_ARCH_ALL)
> >> +
> >> +SRST
> >> +``--pause secs``
> >> + Pause for a number of seconds on entry to main. Useful for attaching
> >> + a debugger after QEMU has been launched by some other entity.
> >> +ERST
> >> +
> >
> > It seems like having an option to race with the debugger is just asking
> > for trouble.
> >
> >> DEF("S", 0, QEMU_OPTION_S, \
> >> "-S freeze CPU at startup (use 'c' to start
> >> execution)\n",
> >> QEMU_ARCH_ALL)
> >> diff --git a/softmmu/vl.c b/softmmu/vl.c
> >> index 8478778..951994f 100644
> >> --- a/softmmu/vl.c
> >> +++ b/softmmu/vl.c
> >> @@ -2844,7 +2844,7 @@ static void create_default_memdev(MachineState *ms,
> >> const char *path)
> >>
> >> void qemu_init(int argc, char **argv, char **envp)
> >> {
> >> - int i;
> >> + int i, seconds;
> >> int snapshot, linux_boot;
> >> const char *initrd_filename;
> >> const char *kernel_filename, *kernel_cmdline;
> >> @@ -2882,6 +2882,13 @@ void qemu_init(int argc, char **argv, char **envp)
> >> QemuPluginList plugin_list = QTAILQ_HEAD_INITIALIZER(plugin_list);
> >> int mem_prealloc = 0; /* force preallocation of physical target
> >> memory */
> >>
> >> + if (getenv("QEMU_PAUSE")) {
> >> + seconds = atoi(getenv("QEMU_PAUSE"));
> >> + printf("Pausing %d seconds for debugger. QEMU PID is %d\n",
> >> + seconds, getpid());
> >> + sleep(seconds);
> >> + }
> >> +
> >> os_set_line_buffering();
> >>
> >> error_init(argv[0]);
> >> @@ -3204,6 +3211,12 @@ void qemu_init(int argc, char **argv, char **envp)
> >> case QEMU_OPTION_gdb:
> >> add_device_config(DEV_GDB, optarg);
> >> break;
> >> + case QEMU_OPTION_pause:
> >> + seconds = atoi(optarg);
> >> + printf("Pausing %d seconds for debugger. QEMU PID is
> >> %d\n",
> >> + seconds, getpid());
> >> + sleep(seconds);
> >> + break;
> >> case QEMU_OPTION_L:
> >> if (is_help_option(optarg)) {
> >> list_data_dirs = true;
> >
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
