Re: [patch 10/10] perf_event_open.2: 4.0 update rdpmc documentation
On Fri, 17 Apr 2015, Andy Lutomirski wrote: > On 04/16/2015 11:20 AM, Vince Weaver wrote: > > Probably a better change would have been to add "2" to mean per-process > > and make that the default setting. Probably too late to fix that now. > > Good point. I wish you'd thought of that sooner :( Well it's been a busy semester and so I've had less time than normal to play perf_event ABI police. I also was surprised this particular patch managed to get into 4.0 so quickly; I thought it was going to be a 4.1 change when I added it to my "changesets to look at more closely" list. In any case most people won't notice this change. It will be a minor inconvenience for HPC people doing complicated homebrew self monitoring (especially if RHEL backports the patch and then suddenly things break and a simple "well are you running 4.0 or newer" is meaningless). Using the value in /sys/devices/cpu/rdpmc to help debug the problem wouldn't have worked anyway because it looks like non-root can't do that. Vince -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 10/10] perf_event_open.2: 4.0 update rdpmc documentation
On Fri, 17 Apr 2015, Andy Lutomirski wrote: On 04/16/2015 11:20 AM, Vince Weaver wrote: Probably a better change would have been to add 2 to mean per-process and make that the default setting. Probably too late to fix that now. Good point. I wish you'd thought of that sooner :( Well it's been a busy semester and so I've had less time than normal to play perf_event ABI police. I also was surprised this particular patch managed to get into 4.0 so quickly; I thought it was going to be a 4.1 change when I added it to my changesets to look at more closely list. In any case most people won't notice this change. It will be a minor inconvenience for HPC people doing complicated homebrew self monitoring (especially if RHEL backports the patch and then suddenly things break and a simple well are you running 4.0 or newer is meaningless). Using the value in /sys/devices/cpu/rdpmc to help debug the problem wouldn't have worked anyway because it looks like non-root can't do that. Vince -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 10/10] perf_event_open.2: 4.0 update rdpmc documentation
On 04/16/2015 11:20 AM, Vince Weaver wrote: The rdpmc instruction allows reading performance counters directly from usersapce. Prior to Linux 4.0 any process could use this instruction when a perf event was running, even if the process itself did not have any open. The following changesets changed the default behavior so that only processes with active events can use rdpmc. Note this change broke the ABI. Previously: /sys/bus/event_source/devices/cpu/rdpmc Set to "1" meant allow across whole system. After the change "2" means the whole system, and "1" means per-process. Probably a better change would have been to add "2" to mean per-process and make that the default setting. Probably too late to fix that now. Good point. I wish you'd thought of that sooner :( --Andy commit a66734297f78707ce39d756b656bfae861d53f62 Author: Andy Lutomirski perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks commit 7911d3f7af14a614617e38245fedf98a724e46a9 Author: Andy Lutomirski perf/x86: Only allow rdpmc if a perf_event is mapped Signed-off-by: Andy Lutomirski Signed-off-by: Peter Zijlstra (Intel) Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Kees Cook Cc: Andrea Arcangeli Cc: Vince Weaver Cc: "hillf.zj" Cc: Valdis Kletnieks Cc: Linus Torvalds Link: http://lkml.kernel.org/r/caac3c1c707dcca48ecbc35f4def21495856f479.1414190806.git.luto-klttt9wpgjjwatoyat5...@public.gmane.org Signed-off-by: Ingo Molnar Signed-off-by: Vince Weaver diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 01ee579..c854d21 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -2377,6 +2377,16 @@ Support for this can be detected with the .I cap_usr_rdpmc field in the mmap page; documentation on how to calculate event values can be found in that section. + +Originally when rdpmc support was enabled, any process (not just ones +with an active perf event) could use the rdpmc instruction to access +the counters. +Starting with Linux 4.0 +.\" 7911d3f7af14a614617e38245fedf98a724e46a9 +rdpmc support is only enabled if an event is currently enabled +in a process' context. +To restore the old behavior, write the value 2 to +.IR /sys/devices/cpu/rdpmc . .SS perf_event ioctl calls .PP Various ioctls act on @@ -2552,11 +2562,18 @@ field of .I perf_event_attr to indicate that you wish to use this PMU. .TP -.IR /sys/bus/event_source/devices/*/rdpmc " (since Linux 3.4)" +.IR /sys/bus/event_source/devices/cpu/rdpmc " (since Linux 3.4)" .\" commit 0c9d42ed4cee2aa1dfc3a260b741baae8615744f If this file is 1, then direct user-space access to the performance counter registers is allowed via the rdpmc instruction. This can be disabled by echoing 0 to the file. + +As of Linux 4.0 +.\" a66734297f78707ce39d756b656bfae861d53f62 +.\" 7911d3f7af14a614617e38245fedf98a724e46a9 +the behavior has changed, so that 1 now means only allow access +to processes with active perf events, with 2 indicating the old +allow-anyone-access behavior. .TP .IR /sys/bus/event_source/devices/*/format/ " (since Linux 3.4)" .\" commit 641cc938815dfd09f8fa1ec72deb814f0938ac33 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwxl29ty76z2rm5m...@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch 10/10] perf_event_open.2: 4.0 update rdpmc documentation
On 04/16/2015 11:20 AM, Vince Weaver wrote: The rdpmc instruction allows reading performance counters directly from usersapce. Prior to Linux 4.0 any process could use this instruction when a perf event was running, even if the process itself did not have any open. The following changesets changed the default behavior so that only processes with active events can use rdpmc. Note this change broke the ABI. Previously: /sys/bus/event_source/devices/cpu/rdpmc Set to 1 meant allow across whole system. After the change 2 means the whole system, and 1 means per-process. Probably a better change would have been to add 2 to mean per-process and make that the default setting. Probably too late to fix that now. Good point. I wish you'd thought of that sooner :( --Andy commit a66734297f78707ce39d756b656bfae861d53f62 Author: Andy Lutomirski luto-klttt9wpgjjwatoyat5...@public.gmane.org perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks commit 7911d3f7af14a614617e38245fedf98a724e46a9 Author: Andy Lutomirski luto-klttt9wpgjjwatoyat5...@public.gmane.org perf/x86: Only allow rdpmc if a perf_event is mapped Signed-off-by: Andy Lutomirski luto-klttt9wpgjjwatoyat5...@public.gmane.org Signed-off-by: Peter Zijlstra (Intel) peterz-wegcikhe2lqwvfeawa7...@public.gmane.org Cc: Paul Mackerras paulus-eunubhrolfbytjvyw6y...@public.gmane.org Cc: Arnaldo Carvalho de Melo acme-dgejt+ai2ygdnm+yrof...@public.gmane.org Cc: Kees Cook keescook-f7+t8e8rja9g9huczpv...@public.gmane.org Cc: Andrea Arcangeli aarcange-h+wxahxf7alqt0dzr+a...@public.gmane.org Cc: Vince Weaver vince-yfjdyhuqu3ostnjn9+b...@public.gmane.org Cc: hillf.zj hillf.zj-gphfcixyaqcqndwcjwf...@public.gmane.org Cc: Valdis Kletnieks valdis.kletnieks-pjaqau27...@public.gmane.org Cc: Linus Torvalds torvalds-de/tnxtf+jlsfhdxvbkv3wd2fqjk+...@public.gmane.org Link: http://lkml.kernel.org/r/caac3c1c707dcca48ecbc35f4def21495856f479.1414190806.git.luto-klttt9wpgjjwatoyat5...@public.gmane.org Signed-off-by: Ingo Molnar mingo-dgejt+ai2ygdnm+yrof...@public.gmane.org Signed-off-by: Vince Weaver vincent.weaver-e7x0jjdqjfghxe+lvdl...@public.gmane.org diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 01ee579..c854d21 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -2377,6 +2377,16 @@ Support for this can be detected with the .I cap_usr_rdpmc field in the mmap page; documentation on how to calculate event values can be found in that section. + +Originally when rdpmc support was enabled, any process (not just ones +with an active perf event) could use the rdpmc instruction to access +the counters. +Starting with Linux 4.0 +.\ 7911d3f7af14a614617e38245fedf98a724e46a9 +rdpmc support is only enabled if an event is currently enabled +in a process' context. +To restore the old behavior, write the value 2 to +.IR /sys/devices/cpu/rdpmc . .SS perf_event ioctl calls .PP Various ioctls act on @@ -2552,11 +2562,18 @@ field of .I perf_event_attr to indicate that you wish to use this PMU. .TP -.IR /sys/bus/event_source/devices/*/rdpmc (since Linux 3.4) +.IR /sys/bus/event_source/devices/cpu/rdpmc (since Linux 3.4) .\ commit 0c9d42ed4cee2aa1dfc3a260b741baae8615744f If this file is 1, then direct user-space access to the performance counter registers is allowed via the rdpmc instruction. This can be disabled by echoing 0 to the file. + +As of Linux 4.0 +.\ a66734297f78707ce39d756b656bfae861d53f62 +.\ 7911d3f7af14a614617e38245fedf98a724e46a9 +the behavior has changed, so that 1 now means only allow access +to processes with active perf events, with 2 indicating the old +allow-anyone-access behavior. .TP .IR /sys/bus/event_source/devices/*/format/ (since Linux 3.4) .\ commit 641cc938815dfd09f8fa1ec72deb814f0938ac33 -- To unsubscribe from this list: send the line unsubscribe linux-man in the body of a message to majordomo-u79uwxl29ty76z2rm5m...@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[patch 10/10] perf_event_open.2: 4.0 update rdpmc documentation
The rdpmc instruction allows reading performance counters directly from usersapce. Prior to Linux 4.0 any process could use this instruction when a perf event was running, even if the process itself did not have any open. The following changesets changed the default behavior so that only processes with active events can use rdpmc. Note this change broke the ABI. Previously: /sys/bus/event_source/devices/cpu/rdpmc Set to "1" meant allow across whole system. After the change "2" means the whole system, and "1" means per-process. Probably a better change would have been to add "2" to mean per-process and make that the default setting. Probably too late to fix that now. commit a66734297f78707ce39d756b656bfae861d53f62 Author: Andy Lutomirski perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks commit 7911d3f7af14a614617e38245fedf98a724e46a9 Author: Andy Lutomirski perf/x86: Only allow rdpmc if a perf_event is mapped Signed-off-by: Andy Lutomirski Signed-off-by: Peter Zijlstra (Intel) Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Kees Cook Cc: Andrea Arcangeli Cc: Vince Weaver Cc: "hillf.zj" Cc: Valdis Kletnieks Cc: Linus Torvalds Link: http://lkml.kernel.org/r/caac3c1c707dcca48ecbc35f4def21495856f479.1414190806.git.l...@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Vince Weaver diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 01ee579..c854d21 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -2377,6 +2377,16 @@ Support for this can be detected with the .I cap_usr_rdpmc field in the mmap page; documentation on how to calculate event values can be found in that section. + +Originally when rdpmc support was enabled, any process (not just ones +with an active perf event) could use the rdpmc instruction to access +the counters. +Starting with Linux 4.0 +.\" 7911d3f7af14a614617e38245fedf98a724e46a9 +rdpmc support is only enabled if an event is currently enabled +in a process' context. +To restore the old behavior, write the value 2 to +.IR /sys/devices/cpu/rdpmc . .SS perf_event ioctl calls .PP Various ioctls act on @@ -2552,11 +2562,18 @@ field of .I perf_event_attr to indicate that you wish to use this PMU. .TP -.IR /sys/bus/event_source/devices/*/rdpmc " (since Linux 3.4)" +.IR /sys/bus/event_source/devices/cpu/rdpmc " (since Linux 3.4)" .\" commit 0c9d42ed4cee2aa1dfc3a260b741baae8615744f If this file is 1, then direct user-space access to the performance counter registers is allowed via the rdpmc instruction. This can be disabled by echoing 0 to the file. + +As of Linux 4.0 +.\" a66734297f78707ce39d756b656bfae861d53f62 +.\" 7911d3f7af14a614617e38245fedf98a724e46a9 +the behavior has changed, so that 1 now means only allow access +to processes with active perf events, with 2 indicating the old +allow-anyone-access behavior. .TP .IR /sys/bus/event_source/devices/*/format/ " (since Linux 3.4)" .\" commit 641cc938815dfd09f8fa1ec72deb814f0938ac33 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[patch 10/10] perf_event_open.2: 4.0 update rdpmc documentation
The rdpmc instruction allows reading performance counters directly from usersapce. Prior to Linux 4.0 any process could use this instruction when a perf event was running, even if the process itself did not have any open. The following changesets changed the default behavior so that only processes with active events can use rdpmc. Note this change broke the ABI. Previously: /sys/bus/event_source/devices/cpu/rdpmc Set to 1 meant allow across whole system. After the change 2 means the whole system, and 1 means per-process. Probably a better change would have been to add 2 to mean per-process and make that the default setting. Probably too late to fix that now. commit a66734297f78707ce39d756b656bfae861d53f62 Author: Andy Lutomirski l...@amacapital.net perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks commit 7911d3f7af14a614617e38245fedf98a724e46a9 Author: Andy Lutomirski l...@amacapital.net perf/x86: Only allow rdpmc if a perf_event is mapped Signed-off-by: Andy Lutomirski l...@amacapital.net Signed-off-by: Peter Zijlstra (Intel) pet...@infradead.org Cc: Paul Mackerras pau...@samba.org Cc: Arnaldo Carvalho de Melo a...@kernel.org Cc: Kees Cook keesc...@chromium.org Cc: Andrea Arcangeli aarca...@redhat.com Cc: Vince Weaver vi...@deater.net Cc: hillf.zj hillf...@alibaba-inc.com Cc: Valdis Kletnieks valdis.kletni...@vt.edu Cc: Linus Torvalds torva...@linux-foundation.org Link: http://lkml.kernel.org/r/caac3c1c707dcca48ecbc35f4def21495856f479.1414190806.git.l...@amacapital.net Signed-off-by: Ingo Molnar mi...@kernel.org Signed-off-by: Vince Weaver vincent.wea...@maine.edu diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 01ee579..c854d21 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -2377,6 +2377,16 @@ Support for this can be detected with the .I cap_usr_rdpmc field in the mmap page; documentation on how to calculate event values can be found in that section. + +Originally when rdpmc support was enabled, any process (not just ones +with an active perf event) could use the rdpmc instruction to access +the counters. +Starting with Linux 4.0 +.\ 7911d3f7af14a614617e38245fedf98a724e46a9 +rdpmc support is only enabled if an event is currently enabled +in a process' context. +To restore the old behavior, write the value 2 to +.IR /sys/devices/cpu/rdpmc . .SS perf_event ioctl calls .PP Various ioctls act on @@ -2552,11 +2562,18 @@ field of .I perf_event_attr to indicate that you wish to use this PMU. .TP -.IR /sys/bus/event_source/devices/*/rdpmc (since Linux 3.4) +.IR /sys/bus/event_source/devices/cpu/rdpmc (since Linux 3.4) .\ commit 0c9d42ed4cee2aa1dfc3a260b741baae8615744f If this file is 1, then direct user-space access to the performance counter registers is allowed via the rdpmc instruction. This can be disabled by echoing 0 to the file. + +As of Linux 4.0 +.\ a66734297f78707ce39d756b656bfae861d53f62 +.\ 7911d3f7af14a614617e38245fedf98a724e46a9 +the behavior has changed, so that 1 now means only allow access +to processes with active perf events, with 2 indicating the old +allow-anyone-access behavior. .TP .IR /sys/bus/event_source/devices/*/format/ (since Linux 3.4) .\ commit 641cc938815dfd09f8fa1ec72deb814f0938ac33 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
