Re: [PATCH] perf: Do not require /lib/modules/* on a guest

From: David Ahern
Date: Mon Jul 29 2013 - 18:41:07 EST

On 7/15/13 2:27 PM, Jason Wessel wrote:
For some types of work loads and special guest environments, you might
have a kernel that has no kernel modules. The perf kvm record tool
fails instantiate vmlinux maps when the kernel modules directory
cannot be opened, even though the kallsyms has been properly
processed. This leads to a perf kvm report that has no guest symbols

Theoretically, use of modules is an option:

if (symbol_conf.use_modules && machine__create_modules(machine) < 0) {

But, the use_modules option was flipped from false to true by b32d133a back in 2009. And the lack of complaints suggests this ominous warning in perf-report, diff and annotate is moot:

OPT_BOOLEAN('m', "modules", &symbol_conf.use_modules,
"load module symbols - WARNING: use only with -k and LIVE kernel"),

This patch changes the failure to locate kernel modules to be

Signed-off-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
tools/perf/util/machine.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index b2ecad6..eb9ebd6 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -808,7 +808,10 @@ static int machine__create_modules(struct machine *machine)

- return machine__set_modules_path(machine);
+ if (machine__set_modules_path(machine) < 0) {
+ pr_debug("Problems setting modules path maps, continuing anyway...\n");
+ }
+ return 0;


Acked-by: David Ahern <dsahern@xxxxxxxxx>

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