perf/x86/amd/ibs: Work around erratum #1197

Erratum #1197 "IBS (Instruction Based Sampling) Register State May be
Incorrect After Restore From CC6" is published in a document:

  "Revision Guide for AMD Family 19h Models 00h-0Fh Processors" 56683 Rev. 1.04 July 2021

  https://bugzilla.kernel.org/show_bug.cgi?id=206537

Implement the erratum's suggested workaround and ignore IBS samples if
MSRC001_1031 == 0.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210817221048.88063-3-kim.phillips@amd.com

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 40669eac9d6db51f09227cd5e8283e79be42bfd0..921f47b9bb247660da174bab9b83c9bb4effbb40 100644 (file)
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -90,6 +90,7 @@ struct perf_ibs {
        unsigned long                   offset_mask[1];
        int                             offset_max;
        unsigned int                    fetch_count_reset_broken : 1;
+       unsigned int                    fetch_ignore_if_zero_rip : 1;
        struct cpu_perf_ibs __percpu    *pcpu;
 
        struct attribute                **format_attrs;
@@ -672,6 +673,10 @@ fail:
        if (check_rip && (ibs_data.regs[2] & IBS_RIP_INVALID)) {
                regs.flags &= ~PERF_EFLAGS_EXACT;
        } else {
+               /* Workaround for erratum #1197 */
+               if (perf_ibs->fetch_ignore_if_zero_rip && !(ibs_data.regs[1]))
+                       goto out;
+
                set_linear_ip(&regs, ibs_data.regs[1]);
                regs.flags |= PERF_EFLAGS_EXACT;
        }
@@ -769,6 +774,9 @@ static __init void perf_event_ibs_init(void)
        if (boot_cpu_data.x86 >= 0x16 && boot_cpu_data.x86 <= 0x18)
                perf_ibs_fetch.fetch_count_reset_broken = 1;
 
+       if (boot_cpu_data.x86 == 0x19 && boot_cpu_data.x86_model < 0x10)
+               perf_ibs_fetch.fetch_ignore_if_zero_rip = 1;
+
        perf_ibs_pmu_init(&perf_ibs_fetch, "ibs_fetch");
 
        if (ibs_caps & IBS_CAPS_OPCNT) {