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    Subject[tip:perf/mce] perf_event, x86, mce: Use TRACE_EVENT() for MCE logging
    Commit-ID:  8968f9d3dc23d9a1821d97c6f11e72a59382e56c
    Gitweb: http://git.kernel.org/tip/8968f9d3dc23d9a1821d97c6f11e72a59382e56c
    Author: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    AuthorDate: Tue, 13 Oct 2009 16:19:41 +0900
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Tue, 13 Oct 2009 09:43:38 +0200

    perf_event, x86, mce: Use TRACE_EVENT() for MCE logging

    This approach is the first baby step towards solving many of the
    structural problems the x86 MCE logging code is having today:

    - It has a private ring-buffer implementation that has a number
    of limitations and has been historically fragile and buggy.

    - It is using a quirky /dev/mcelog ioctl driven ABI that is MCE
    specific. /dev/mcelog is not part of any larger logging
    framework and hence has remained on the fringes for many years.

    - The MCE logging code is still very unclean partly due to its ABI
    limitations. Fields are being reused for multiple purposes, and
    the whole message structure is limited and x86 specific to begin
    with.

    All in one, the x86 tree would like to move away from this private
    implementation of an event logging facility to a broader framework.

    By using perf events we gain the following advantages:

    - Multiple user-space agents can access MCE events. We can have an
    mcelog daemon running but also a system-wide tracer capturing
    important events in flight-recorder mode.

    - Sampling support: the kernel and the user-space call-chain of MCE
    events can be stored and analyzed as well. This way actual patterns
    of bad behavior can be matched to precisely what kind of activity
    happened in the kernel (and/or in the app) around that moment in
    time.

    - Coupling with other hardware and software events: the PMU can track a
    number of other anomalies - monitoring software might chose to
    monitor those plus the MCE events as well - in one coherent stream of
    events.

    - Discovery of MCE sources - tracepoints are enumerated and tools can
    act upon the existence (or non-existence) of various channels of MCE
    information.

    - Filtering support: we just subscribe to and act upon the events we
    are interested in. Then even on a per event source basis there's
    in-kernel filter expressions available that can restrict the amount
    of data that hits the event channel.

    - Arbitrary deep per cpu buffering of events - we can buffer 32
    entries or we can buffer as much as we want, as long as we have
    the RAM.

    - An NMI-safe ring-buffer implementation - mappable to user-space.

    - Built-in support for timestamping of events, PID markers, CPU
    markers, etc.

    - A rich ABI accessible over system call interface. Per cpu, per task
    and per workload monitoring of MCE events can be done this way. The
    ABI itself has a nice, meaningful structure.

    - Extensible ABI: new fields can be added without breaking tooling.
    New tracepoints can be added as the hardware side evolves. There's
    various parsers that can be used.

    - Lots of scheduling/buffering/batching modes of operandi for MCE
    events. poll() support. mmap() support. read() support. You name it.

    - Rich tooling support: even without any MCE specific extensions added
    the 'perf' tool today offers various views of MCE data: perf report,
    perf stat, perf trace can all be used to view logged MCE events and
    perhaps correlate them to certain user-space usage patterns. But it
    can be used directly as well, for user-space agents and policy action
    in mcelog, etc.

    With this we hope to achieve significant code cleanup and feature
    improvements in the MCE code, and we hope to be able to drop the
    /dev/mcelog facility in the end.

    This patch is just a plain dumb dump of mce_log() records to
    the tracepoints / perf events framework - a first proof of
    concept step.

    Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    Cc: Huang Ying <ying.huang@intel.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    LKML-Reference: <4AD42A0D.7050104@jp.fujitsu.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    arch/x86/kernel/cpu/mcheck/mce.c | 6 +++
    include/trace/events/mce.h | 69 ++++++++++++++++++++++++++++++++++++++
    2 files changed, 75 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
    index b1598a9..39caea3 100644
    --- a/arch/x86/kernel/cpu/mcheck/mce.c
    +++ b/arch/x86/kernel/cpu/mcheck/mce.c
    @@ -46,6 +46,9 @@

    #include "mce-internal.h"

    +#define CREATE_TRACE_POINTS
    +#include <trace/events/mce.h>
    +
    int mce_disabled __read_mostly;

    #define MISC_MCELOG_MINOR 227
    @@ -141,6 +144,9 @@ void mce_log(struct mce *mce)
    {
    unsigned next, entry;

    + /* Emit the trace record: */
    + trace_mce_record(mce);
    +
    mce->finished = 0;
    wmb();
    for (;;) {
    diff --git a/include/trace/events/mce.h b/include/trace/events/mce.h
    new file mode 100644
    index 0000000..7eee778
    --- /dev/null
    +++ b/include/trace/events/mce.h
    @@ -0,0 +1,69 @@
    +#undef TRACE_SYSTEM
    +#define TRACE_SYSTEM mce
    +
    +#if !defined(_TRACE_MCE_H) || defined(TRACE_HEADER_MULTI_READ)
    +#define _TRACE_MCE_H
    +
    +#include <linux/ktime.h>
    +#include <linux/tracepoint.h>
    +#include <asm/mce.h>
    +
    +TRACE_EVENT(mce_record,
    +
    + TP_PROTO(struct mce *m),
    +
    + TP_ARGS(m),
    +
    + TP_STRUCT__entry(
    + __field( u64, mcgcap )
    + __field( u64, mcgstatus )
    + __field( u8, bank )
    + __field( u64, status )
    + __field( u64, addr )
    + __field( u64, misc )
    + __field( u64, ip )
    + __field( u8, cs )
    + __field( u64, tsc )
    + __field( u64, walltime )
    + __field( u32, cpu )
    + __field( u32, cpuid )
    + __field( u32, apicid )
    + __field( u32, socketid )
    + __field( u8, cpuvendor )
    + ),
    +
    + TP_fast_assign(
    + __entry->mcgcap = m->mcgcap;
    + __entry->mcgstatus = m->mcgstatus;
    + __entry->bank = m->bank;
    + __entry->status = m->status;
    + __entry->addr = m->addr;
    + __entry->misc = m->misc;
    + __entry->ip = m->ip;
    + __entry->cs = m->cs;
    + __entry->tsc = m->tsc;
    + __entry->walltime = m->time;
    + __entry->cpu = m->extcpu;
    + __entry->cpuid = m->cpuid;
    + __entry->apicid = m->apicid;
    + __entry->socketid = m->socketid;
    + __entry->cpuvendor = m->cpuvendor;
    + ),
    +
    + TP_printk("CPU: %d, MCGc/s: %llx/%llx, MC%d: %016Lx, ADDR/MISC: %016Lx/%016Lx, RIP: %02x:<%016Lx>, TSC: %llx, PROCESSOR: %u:%x, TIME: %llu, SOCKET: %u, APIC: %x",
    + __entry->cpu,
    + __entry->mcgcap, __entry->mcgstatus,
    + __entry->bank, __entry->status,
    + __entry->addr, __entry->misc,
    + __entry->cs, __entry->ip,
    + __entry->tsc,
    + __entry->cpuvendor, __entry->cpuid,
    + __entry->walltime,
    + __entry->socketid,
    + __entry->apicid)
    +);
    +
    +#endif /* _TRACE_MCE_H */
    +
    +/* This part must be outside protection */
    +#include <trace/define_trace.h>

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