oprofile: re-add force_arch_perfmon option

This re-adds the force_arch_perfmon option that was in the original
arch perfmon patchkit. Originally this was rejected in favour
of a generalized perfmon=name option, but it turned out implementing
the later in a reliable way is hard (and it would have been easy
to crash the kernel if a user gets it wrong)

But now Atom and Core i7 support being readded a user would
need to update their oprofile userland to beyond 0.9.4 to use oprofile again
on Atom or Core i7.

To avoid this problem readd the force_arch_perfmon option.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 90b3924..9b9566b 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1650,6 +1650,12 @@ and is between 256 and 4096 characters. It is defined in the file
        oprofile.timer= [HW]
                        Use timer interrupt instead of performance counters
 
+       oprofile.force_arch_perfmon=1   [X86]
+                       Force use of architectural perfmon instead of
+                       the CPU specific event set.
+                       This might be useful if you have older oprofile
+                       userland or if you want common events over Intel CPUs.
+
        osst=           [HW,SCSI] SCSI Tape Driver
                        Format: <buffer_size>,<write_threshold>
                        See also Documentation/scsi/st.txt.

diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index 202864a..e5171c9 100644 (file)
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -389,10 +389,16 @@ static int __init p4_init(char **cpu_type)
        return 0;
 }
 
+int force_arch_perfmon;
+module_param(force_arch_perfmon, int, 0);
+
 static int __init ppro_init(char **cpu_type)
 {
        __u8 cpu_model = boot_cpu_data.x86_model;
 
+       if (force_arch_perfmon && cpu_has_arch_perfmon)
+               return 0;
+
        switch (cpu_model) {
        case 0 ... 2:
                *cpu_type = "i386/ppro";