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.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>