[PATCH v1 7/9] x86/resctrl: Assign HW RMIDs to CPUs for soft RMID

Peter Newman
2023-04-21T14:19:06Z

To implement soft RMIDs, each CPU needs a HW RMID that is unique within
its L3 cache domain. This is the minimum number of RMIDs needed to
monitor all CPUs.

This is accomplished by determining the rank of each CPU's mask bit
within its L3 shared_cpu_mask in resctrl_online_cpu().

Signed-off-by: Peter Newman <peternewman@google.com>
---
arch/x86/kernel/cpu/resctrl/core.c | 39 +++++++++++++++++++++++++++++-
1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 47b1c37a81f8..b0d873231b1e 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -596,6 +596,38 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
}
}

+/* Assign each CPU an RMID that is unique within its cache domain. */
+static u32 determine_hw_rmid_for_cpu(int cpu)
+{
+ struct cpu_cacheinfo *ci = get_cpu_cacheinfo(cpu);
+ struct cacheinfo *l3ci = NULL;
+ u32 rmid;
+ int i;
+
+ /* Locate the cacheinfo for this CPU's L3 cache. */
+ for (i = 0; i < ci->num_leaves; i++) {
+ if (ci->info_list[i].level == 3 &&
+ (ci->info_list[i].attributes & CACHE_ID)) {
+ l3ci = &ci->info_list[i];
+ break;
+ }
+ }
+ WARN_ON(!l3ci);
+
+ if (!l3ci)
+ return 0;
+
+ /* Use the position of cpu in its shared_cpu_mask as its RMID. */
+ rmid = 0;
+ for_each_cpu(i, &l3ci->shared_cpu_map) {
+ if (i == cpu)
+ break;
+ rmid++;
+ }
+
+ return rmid;
+}
+
static void clear_closid_rmid(int cpu)
{
struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);
@@ -604,7 +636,12 @@ static void clear_closid_rmid(int cpu)
state->default_rmid = 0;
state->cur_closid = 0;
state->cur_rmid = 0;
- wrmsr(MSR_IA32_PQR_ASSOC, 0, 0);
+ state->hw_rmid = 0;
+
+ if (static_branch_likely(&rdt_soft_rmid_enable_key))
+ state->hw_rmid = determine_hw_rmid_for_cpu(cpu);
+
+ wrmsr(MSR_IA32_PQR_ASSOC, state->hw_rmid, 0);
}

static int resctrl_online_cpu(unsigned int cpu)
--
2.40.0.634.g4ca3ef3211-goog