[PATCH v5 0/2] x86/resctrl: Pass domain to target CPU

Tony Luck
2024-03-08T21:38:56Z

reset_all_ctrls() and resctrl_arch_update_domains() use on_each_cpu_mask()
to call rdt_ctrl_update() on potentially one CPU from each domain.

But this means rdt_ctrl_update() needs to figure out which domain to
apply changes to. Doing so requires a search of all domains in a resource,
which can only be done safely if cpus_lock is held. Both callers do hold
this lock, but there isn't a way for a function called on another CPU
via IPI to verify this.

Commit c0d848fcb09d ("x86/resctrl: Remove lockdep annotation that triggers
false positive") removed the incorrect assertions.

Add the target domain to the msr_param structure and
call rdt_ctrl_update() for each domain separately using
smp_call_function_single(). This means that rdt_ctrl_update() doesn't
need to search for the domain and get_domain_from_cpu() can safely assert
that the cpus_lock is held since the remaining callers do not use IPI.

Signed-off-by: Tony Luck <tony.luck@intel.com>

---
Changes since V4: Link: https://lore.kernel.org/all/20240228193717.8170-1-tony.luck@intel.com/

Reinette: Only assign "cpu" once in resctrl_arch_update_domains() [but
see change from James below]

James: Use smp_call_function_any() instead of cpumask_any() +
smp_call_function_single() to avoid unnecessary IPI in both
resctrl_arch_update_domains() and reset_all_ctrls(). This
eliminates a need for the "cpu" local variable.

Tony Luck (2):
x86/resctrl: Pass domain to target CPU
x86/resctrl: Simplify call convention for MSR update functions

arch/x86/kernel/cpu/resctrl/internal.h | 5 ++-
arch/x86/kernel/cpu/resctrl/core.c | 55 +++++++++--------------
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 40 ++++-------------
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 12 +----
4 files changed, 34 insertions(+), 78 deletions(-)

base-commit: c0d848fcb09d80a5f48b99f85e448185125ef59f
--
2.43.0