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    Subject[PATCH v3 15/21] x86/resctrl: Abstract __rmid_read()
    Date
    __rmid_read() selects the specified eventid and returns the counter
    value from the MSR. The error handling is architecture specific, and
    handled by the callers, rdtgroup_mondata_show() and __mon_event_count().

    Error handling should be handled by architecture specific code, as
    a different architecture may have different requirements. MPAM's
    counters can report that they are 'not ready', requiring a second
    read after a short delay. This should be hidden from resctrl.

    Make __rmid_read() the architecture specific function for reading
    a counter. Rename it resctrl_arch_rmid_read() and move the error
    handling into it.

    Signed-off-by: James Morse <james.morse@arm.com>
    ---
    Changes since v2:
    * Capitalisation
    * Stray newline restored
    * Removed rr->val set to the error value, and replaced it with clearing the
    the error to hide Unavailable from monitor group reads. (and added a block
    comment).

    Changes since v1:
    * Return EINVAL from the impossible case in __mon_event_count() instead
    of an x86 hardware specific value.
    ---
    arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 4 +-
    arch/x86/kernel/cpu/resctrl/internal.h | 1 +
    arch/x86/kernel/cpu/resctrl/monitor.c | 53 +++++++++++++++--------
    include/linux/resctrl.h | 1 +
    4 files changed, 39 insertions(+), 20 deletions(-)

    diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
    index ece3a1e0e6f2..d3f7eb2ac14b 100644
    --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
    +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
    @@ -579,9 +579,9 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)

    mon_event_read(&rr, r, d, rdtgrp, evtid, false);

    - if (rr.val & RMID_VAL_ERROR)
    + if (rr.err == -EIO)
    seq_puts(m, "Error\n");
    - else if (rr.val & RMID_VAL_UNAVAIL)
    + else if (rr.err == -EINVAL)
    seq_puts(m, "Unavailable\n");
    else
    seq_printf(m, "%llu\n", rr.val * hw_res->mon_scale);
    diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
    index 726065bc02e4..e55d1774ce9c 100644
    --- a/arch/x86/kernel/cpu/resctrl/internal.h
    +++ b/arch/x86/kernel/cpu/resctrl/internal.h
    @@ -94,6 +94,7 @@ struct rmid_read {
    struct rdt_domain *d;
    enum resctrl_event_id evtid;
    bool first;
    + int err;
    u64 val;
    };

    diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
    index 431acc3d3eb8..b6ad290fda8d 100644
    --- a/arch/x86/kernel/cpu/resctrl/monitor.c
    +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
    @@ -167,9 +167,9 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
    memset(am, 0, sizeof(*am));
    }

    -static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
    +int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *val)
    {
    - u64 val;
    + u64 msr_val;

    /*
    * As per the SDM, when IA32_QM_EVTSEL.EvtID (bits 7:0) is configured
    @@ -180,14 +180,24 @@ static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
    * are error bits.
    */
    wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
    - rdmsrl(MSR_IA32_QM_CTR, val);
    + rdmsrl(MSR_IA32_QM_CTR, msr_val);

    - return val;
    + if (msr_val & RMID_VAL_ERROR)
    + return -EIO;
    + if (msr_val & RMID_VAL_UNAVAIL)
    + return -EINVAL;
    +
    + *val = msr_val;
    +
    + return 0;
    }

    static bool rmid_dirty(struct rmid_entry *entry)
    {
    - u64 val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
    + u64 val = 0;
    +
    + if (resctrl_arch_rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID, &val))
    + return true;

    return val >= resctrl_cqm_threshold;
    }
    @@ -259,8 +269,8 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
    {
    struct rdt_resource *r;
    struct rdt_domain *d;
    - int cpu;
    - u64 val;
    + int cpu, err;
    + u64 val = 0;

    r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;

    @@ -268,8 +278,10 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
    cpu = get_cpu();
    list_for_each_entry(d, &r->domains, list) {
    if (cpumask_test_cpu(cpu, &d->cpu_mask)) {
    - val = __rmid_read(entry->rmid, QOS_L3_OCCUP_EVENT_ID);
    - if (val <= resctrl_cqm_threshold)
    + err = resctrl_arch_rmid_read(entry->rmid,
    + QOS_L3_OCCUP_EVENT_ID,
    + &val);
    + if (err || val <= resctrl_cqm_threshold)
    continue;
    }

    @@ -319,15 +331,15 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
    {
    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(rr->r);
    struct mbm_state *m;
    - u64 chunks, tval;
    + u64 chunks, tval = 0;

    if (rr->first)
    resctrl_arch_reset_rmid(rr->r, rr->d, rmid, rr->evtid);

    - tval = __rmid_read(rmid, rr->evtid);
    - if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
    - return tval;
    - }
    + rr->err = resctrl_arch_rmid_read(rmid, rr->evtid, &tval);
    + if (rr->err)
    + return rr->err;
    +
    switch (rr->evtid) {
    case QOS_L3_OCCUP_EVENT_ID:
    rr->val += tval;
    @@ -343,7 +355,7 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
    * Code would never reach here because an invalid
    * event id would fail the __rmid_read.
    */
    - return RMID_VAL_ERROR;
    + return -EINVAL;
    }

    if (rr->first) {
    @@ -419,9 +431,14 @@ void mon_event_count(void *info)
    }
    }

    - /* Report error if none of rmid_reads are successful */
    - if (ret_val)
    - rr->val = ret_val;
    + /*
    + * __mon_event_count() calls for newly created monitor groups may
    + * report -EINVAL/Unavailable if the monitor hasn't seen any traffic.
    + * If the first call for the control group succeed, discard any error
    + * set by reads of monitor groups.
    + */
    + if (ret_val == 0)
    + rr->err = 0;
    }

    /*
    diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
    index 0b48239f5920..70112dbfa128 100644
    --- a/include/linux/resctrl.h
    +++ b/include/linux/resctrl.h
    @@ -219,6 +219,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_domain *d,
    u32 closid, enum resctrl_conf_type type);
    int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d);
    void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d);
    +int resctrl_arch_rmid_read(u32 rmid, enum resctrl_event_id eventid, u64 *res);

    /**
    * resctrl_arch_reset_rmid() - Reset any private state associated with rmid
    --
    2.30.2
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