d4097f1937
Similar to what is in 'perf record', works just like there:
# perf trace -e msr:*
328.297 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.302 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.306 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.317 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.322 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.327 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.331 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.336 :0/0 msr:write_msr(msr: FS_BASE, val: 140240388381888)
328.340 :0/0 ^Cmsr:write_msr(msr: FS_BASE, val: 140240388381888)
#
So, for a system wide trace session looking at the write_msr tracepoint
we see a flood of MSR_FS_BASE, we need to get the number for that:
# grep FS_BASE /tmp/build/perf/trace/beauty/generated/x86_arch_MSRs_array.c
[0xc0000100 - x86_64_specific_MSRs_offset] = "FS_BASE",
#
And then use it in a filter:
# perf trace -e msr:* --filter="msr!=0xc0000100"
<SNIP>
942.177 :0/0 msr:write_msr(msr: IA32_TSC_DEADLINE, val: 3056931068232)
942.199 :0/0 msr:write_msr(msr: IA32_TSC_DEADLINE, val: 3057135655252)
942.203 :0/0 msr:write_msr(msr: IA32_TSC_DEADLINE, val: 3056931068222)
942.231 :0/0 msr:write_msr(msr: IA32_TSC_DEADLINE, val: 3056998373022)
942.241 :0/0 msr:write_msr(msr: IA32_TSC_DEADLINE, val: 3056931068236)
<SNIP>
#
Ok, lets filter that too, too noisy:
# grep TSC_DEADLINE /tmp/build/perf/trace/beauty/generated/x86_arch_MSRs_array.c
[0x000006E0] = "IA32_TSC_DEADLINE",
#
# perf trace -e msr:* --filter="msr!=0xc0000100 && msr!=0x6e0" -a sleep 0.1
0.000 :0/0 msr:read_msr(msr: IA32_TSC_ADJUST)
0.066 CPU 0/KVM/4895 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
0.070 CPU 0/KVM/4895 msr:write_msr(msr: 0x830, val: 34359740667)
0.099 CPU 0/KVM/4895 msr:read_msr(msr: IA32_SYSENTER_ESP, val: -2199021993472)
0.100 CPU 0/KVM/4895 msr:read_msr(msr: IA32_APICBASE, val: 4276096000)
0.101 CPU 0/KVM/4895 msr:read_msr(msr: IA32_DEBUGCTLMSR)
0.109 :0/0 msr:write_msr(msr: IA32_SPEC_CTRL)
1.000 :0/0 msr:write_msr(msr: 0x830, val: 17179871485)
18.893 :0/0 msr:write_msr(msr: 0x83f, val: 246)
28.810 :0/0 msr:write_msr(msr: 0x830, val: 68719479037)
40.117 CPU 0/KVM/4895 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
40.127 CPU 0/KVM/4895 msr:read_msr(msr: IA32_DEBUGCTLMSR)
40.139 CPU 0/KVM/4895 msr:write_msr(msr: LSTAR, val: -2130661312)
40.141 CPU 0/KVM/4895 msr:write_msr(msr: SYSCALL_MASK, val: 14080)
40.142 CPU 0/KVM/4895 msr:write_msr(msr: TSC_AUX)
40.144 CPU 0/KVM/4895 msr:write_msr(msr: KERNEL_GS_BASE)
40.147 CPU 0/KVM/4895 msr:write_msr(msr: IA32_SPEC_CTRL)
40.148 CPU 0/KVM/4895 msr:write_msr(msr: IA32_FLUSH_CMD, val: 1)
40.151 CPU 0/KVM/4895 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
^C
#
One can combine that with filtering pids as well:
# perf trace -e msr:* --filter="msr!=0xc0000100 && msr!=0x6e0" --filter-pids 4895 -a sleep 0.09
0.000 :0/0 msr:write_msr(msr: 0x830, val: 4294969597)
0.291 gnome-terminal/2790 msr:write_msr(msr: SYSCALL_MASK, val: 292608)
0.294 gnome-terminal/2790 msr:write_msr(msr: LSTAR, val: -1935671280)
0.295 gnome-terminal/2790 msr:write_msr(msr: TSC_AUX, val: 6)
10.940 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 4294969597)
15.943 gnome-shell/2096 msr:write_msr(msr: 0x830, val: 4294969597)
16.975 :0/0 msr:write_msr(msr: 0x830, val: 4294969597)
19.560 :0/0 msr:write_msr(msr: 0x83f, val: 246)
25.162 :0/0 msr:read_msr(msr: IA32_TSC_ADJUST)
25.807 JS Watchdog/3635 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
25.820 :0/0 msr:write_msr(msr: IA32_SPEC_CTRL)
25.941 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 4294969597)
26.941 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 4294969597)
29.942 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 4294969597)
45.313 :0/0 msr:write_msr(msr: 0x83f, val: 246)
56.945 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 4294969597)
60.946 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 4294969597)
74.096 JS Watchdog/8971 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
74.130 :0/0 msr:write_msr(msr: IA32_SPEC_CTRL)
79.673 :0/0 msr:write_msr(msr: 0x83f, val: 246)
79.947 gnome-terminal/2790 msr:write_msr(msr: 0x830, val: 17179871485)
#
Or for just a pid, with callchains:
# grep SYSCALL_MAS /tmp/build/perf/trace/beauty/generated/x86_arch_MSRs_array.c
[0xc0000084 - x86_64_specific_MSRs_offset] = "SYSCALL_MASK",
# perf trace -e msr:* --filter="msr==0xc0000084" --pid 2790 --call-graph=dwarf
0.000 gnome-terminal/2790 msr:write_msr(msr: SYSCALL_MASK, val: 292608)
do_trace_write_msr ([kernel.kallsyms])
do_trace_write_msr ([kernel.kallsyms])
kvm_on_user_return ([kvm])
fire_user_return_notifiers ([kernel.kallsyms])
exit_to_usermode_loop ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64 ([kernel.kallsyms])
__GI___poll (inlined)
9299.073 gnome-terminal/2790 msr:write_msr(msr: SYSCALL_MASK, val: 292608)
do_trace_write_msr ([kernel.kallsyms])
do_trace_write_msr ([kernel.kallsyms])
kvm_on_user_return ([kvm])
fire_user_return_notifiers ([kernel.kallsyms])
exit_to_usermode_loop ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64 ([kernel.kallsyms])
__GI___poll (inlined)
9348.374 gnome-terminal/2790 msr:write_msr(msr: SYSCALL_MASK, val: 292608)
do_trace_write_msr ([kernel.kallsyms])
do_trace_write_msr ([kernel.kallsyms])
kvm_on_user_return ([kvm])
fire_user_return_notifiers ([kernel.kallsyms])
exit_to_usermode_loop ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64 ([kernel.kallsyms])
__GI___poll (inlined)
<SNIP>
#
Ok, just another form of KVM to emit MSRs :-)
Next step: elliminate those greps by getting the filter expression,
looking for arg names, then for the arrays associated with it to do a
reverse lookup.
Also allow those filters to be associated with strace-like syscall
names.
After that: augment the 'val' arg for 'msr:write_msr' based on the first
arg, 'msr'.
Then, do that with eBPF too, not just with tracepoint filters.
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-95bfe5d4tzy5f66bx49d05rj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.