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    SubjectRe: [PATCH v1 05/31] x86/resctrl: Remove rdtgroup from update_cpu_closid_rmid()
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    Hi James,

    On 3/21/2024 9:50 AM, James Morse wrote:
    > update_cpu_closid_rmid() takes a struct rdtgroup as an argument, which
    > it uses to update the local CPUs default pqr values. This is a problem
    > once the resctrl parts move out to /fs/, as the arch code cannot
    > poke around inside struct rdtgroup.
    >
    > Rename update_cpu_closid_rmid() as resctrl_arch_sync_cpus_defaults()
    > to be used as the target of an IPI, and pass the effective CLOSID
    > and RMID in a new struct.
    >
    > Signed-off-by: James Morse <james.morse@arm.com>
    > ---
    > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 +++++++++++++++----
    > include/linux/resctrl.h | 11 +++++++++++
    > 2 files changed, 26 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
    > index 5d2c1ce5b6b1..18f097fce51e 100644
    > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
    > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
    > @@ -341,13 +341,13 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of,
    > * from update_closid_rmid() is protected against __switch_to() because
    > * preemption is disabled.
    > */
    > -static void update_cpu_closid_rmid(void *info)
    > +void resctrl_arch_sync_cpu_defaults(void *info)
    > {
    > - struct rdtgroup *r = info;
    > + struct resctrl_cpu_sync *r = info;
    >
    > if (r) {
    > this_cpu_write(pqr_state.default_closid, r->closid);
    > - this_cpu_write(pqr_state.default_rmid, r->mon.rmid);
    > + this_cpu_write(pqr_state.default_rmid, r->rmid);
    > }
    >
    > /*
    > @@ -362,11 +362,22 @@ static void update_cpu_closid_rmid(void *info)
    > * Update the PGR_ASSOC MSR on all cpus in @cpu_mask,
    > *
    > * Per task closids/rmids must have been set up before calling this function.
    > + * @r may be NULL.
    > */
    > static void
    > update_closid_rmid(const struct cpumask *cpu_mask, struct rdtgroup *r)
    > {
    > - on_each_cpu_mask(cpu_mask, update_cpu_closid_rmid, r, 1);
    > + struct resctrl_cpu_sync defaults;
    > + struct resctrl_cpu_sync *defaults_p = NULL;

    Please maintain reverse fir order.

    > +
    > + if (r) {
    > + defaults.closid = r->closid;
    > + defaults.rmid = r->mon.rmid;
    > + defaults_p = &defaults;
    > + }
    > +
    > + on_each_cpu_mask(cpu_mask, resctrl_arch_sync_cpu_defaults, defaults_p,
    > + 1);
    > }
    >
    > static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
    > diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
    > index 6e87bc95f5ea..2b79e4159507 100644
    > --- a/include/linux/resctrl.h
    > +++ b/include/linux/resctrl.h
    > @@ -220,6 +220,17 @@ struct resctrl_schema {
    > u32 num_closid;
    > };
    >
    > +struct resctrl_cpu_sync {
    > + u32 closid;
    > + u32 rmid;
    > +};
    > +
    > +/*
    > + * Update and re-load this CPUs defaults. Called via IPI, takes a pointer to

    "this CPU's defaults"?

    > + * struct resctrl_cpu_sync, or NULL.
    > + */

    Updating the CPU's defaults is not the primary goal of this function and because
    of that I do not think this should be the focus with the main goal (updating
    RMID and CLOSID on CPU) ignored. Specifically, this function only updates
    the defaults if *info is set but it _always_ ensures CPU is running with
    appropriate CLOSID/RMID (which may or may not be from a CPU default).

    I think resctrl_arch_sync_cpu_closid_rmid() may be more appropriate
    and the comment needs to elaborate what the function does.

    > +void resctrl_arch_sync_cpu_defaults(void *info);
    > +
    > /* The number of closid supported by this resource regardless of CDP */
    > u32 resctrl_arch_get_num_closid(struct rdt_resource *r);
    > int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid);

    Reinette

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