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package/qemu: add option to enable tracing (default no)

PATCH Applied [email protected] 2 participants 2 messages Jul 12, 2023 – Sep 2, 2023

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PATCH 1/1 package/qemu: add option to enable tracing (default no)

From: Carlos Santos <[email protected]>

Tracing is a development feature for debugging, profiling, and observing QEMU execution. It does not make sense to enable it by default, so add a config to enable the "log" tracing backend (the default one). Options to select other backends may be added in the future.

Also pull a patch already reviewed upstream to install the trace events file only if necessary:

    https://patchwork.kernel.org/project/qemu-devel/patch/[email protected]/
Signed-off-by Carlos Santos <[email protected]>
---
 ...-trace-events-file-only-if-necessary.patch | 29 +++++++++++++++++++
 package/qemu/Config.in                        |  9 ++++++
 package/qemu/qemu.mk                          |  6 ++++
 3 files changed, 44 insertions(+)
 create mode 100644 package/qemu/0004-tracing-install-trace-events-file-only-if-necessary.patch
package/qemu/0004-tracing-install-trace-events-file-only-if-necessary.patch new file +29 -0
new file mode 100644
index 0000000000..0db9a6b647
@@ -0,0 +1,29 @@
+From 5c43da1e4983cc3c209b325a5228b6149e0a0ccf Mon Sep 17 00:00:00 2001
+From: Carlos Santos <[email protected]>
+Date: Fri, 24 Mar 2023 21:40:22 -0300
+Subject: [PATCH] tracing: install trace events file only if necessary
+
+It is not useful when configuring with --enable-trace-backends=nop.
+
+Signed-off-by: Carlos Santos <[email protected]>
+Signed-off-by: Carlos Santos <[email protected]>
+---
+ trace/meson.build | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/trace/meson.build b/trace/meson.build
+index 8e80be895c..30b1d942eb 100644
+--- a/trace/meson.build
++++ b/trace/meson.build
+@@ -64,7 +64,7 @@ trace_events_all = custom_target('trace-events-all',
+                                  input: trace_events_files,
+                                  command: [ 'cat', '@INPUT@' ],
+                                  capture: true,
+-                                 install: true,
++                                 install: get_option('trace_backends') != [ 'nop' ],
+                                  install_dir: qemu_datadir)
+ 
+ if 'ust' in get_option('trace_backends')
+-- 
+2.31.1
+
package/qemu/Config.in +9 -0
index 6fb34a0dae..8d53ced300 100644
@@ -106,6 +106,15 @@ config BR2_PACKAGE_QEMU_FDT
 	  Say 'y' here to have QEMU capable of constructing Device
 	  Trees, and passing them to the VMs.
 
+config BR2_PACKAGE_QEMU_TRACING
+	bool "Enable tracing"
+	help
+	  Say 'y' to enable the "log" tracing infrastructure in QEMU,
+	  used for debugging, profiling, and observing execution. For
+	  detailed documentation, see
+
+	  https://www.qemu.org/docs/master/devel/tracing.html
+
 endif # BR2_PACKAGE_QEMU_SYSTEM
 
 comment "systems emulation needs a toolchain w/ dynamic library"
package/qemu/qemu.mk +6 -0
index c530896fa8..a020dd5226 100644
@@ -159,6 +159,12 @@ else
 QEMU_OPTS += --disable-fdt
 endif
 
+ifeq ($(BR2_PACKAGE_QEMU_TRACING),y)
+QEMU_OPTS += --enable-trace-backends=log
+else
+QEMU_OPTS += --enable-trace-backends=nop
+endif
+
 ifeq ($(BR2_PACKAGE_QEMU_TOOLS),y)
 QEMU_OPTS += --enable-tools
 else
Signature · 6 lines
2.39.3

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Applied
#1 lore raw

Hello Carlos,

Quoted 12 lines · On Wed, 12 Jul 2023 19:01:19 -0300 [email protected] wrote:

From: Carlos Santos <[email protected]>

Tracing is a development feature for debugging, profiling, and observing QEMU execution. It does not make sense to enable it by default, so add a config to enable the "log" tracing backend (the default one). Options to select other backends may be added in the future.

Also pull a patch already reviewed upstream to install the trace events file only if necessary:

    https://patchwork.kernel.org/project/qemu-devel/patch/[email protected]/
Quoted 7 lines
Signed-off-by Carlos Santos <[email protected]>
---
 ...-trace-events-file-only-if-necessary.patch | 29 +++++++++++++++++++
 package/qemu/Config.in                        |  9 ++++++
 package/qemu/qemu.mk                          |  6 ++++
 3 files changed, 44 insertions(+)
 create mode 100644 package/qemu/0004-tracing-install-trace-events-file-only-if-necessary.patch

Applied to next after adding an "Upstream:" tag inside the patch, which we now require (you get a "make check-package" warning if you don't have this tag).

Thanks a lot!

Thomas

Signature · 7 lines
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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