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    Subject[PATCH 4.14 007/217] perf/x86/amd/ibs: Work around erratum #1197
    Date
    From: Kim Phillips <kim.phillips@amd.com>

    [ Upstream commit 26db2e0c51fe83e1dd852c1321407835b481806e ]

    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
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/events/amd/ibs.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
    index 3fe68f7f9d5e..5043425ced6b 100644
    --- 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;
    @@ -674,6 +675,10 @@ 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;
    }
    @@ -767,6 +772,9 @@ 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) {
    --
    2.30.2


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