[PATCH v4 20/21] x86/resctrl: Add resctrl_rmid_realloc_limit to abstract x86's boot_cpu_data

[James Morse <james.morse@arm.com>]

resctrl_rmid_realloc_threshold can be set by user-space. The maximum
value is specified by the architecture.

Currently max_threshold_occ_write() reads the maximum value from
boot_cpu_data.x86_cache_size, which is not portable to another
architecture.

Add resctrl_rmid_realloc_limit to describe the maximum size in bytes
that user-space can set the threshold to.

Reviewed-by: Jamie Iles <quic_jiles@quicinc.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/x86/kernel/cpu/resctrl/monitor.c  | 9 +++++++--
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 2 +-
 include/linux/resctrl.h                | 1 +
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 00f6e27e4e0d..bc5c31920a66 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -64,6 +64,11 @@ unsigned int rdt_mon_features;
  */
 unsigned int resctrl_rmid_realloc_threshold;
 
+/*
+ * This is the maximum value for the reallocation threshold, in bytes.
+ */
+unsigned int resctrl_rmid_realloc_limit;
+
 #define CF(cf)	((unsigned long)(1048576 * (cf) + 0.5))
 
 /*
@@ -744,10 +749,10 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
 {
 	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
 	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
-	unsigned int cl_size = boot_cpu_data.x86_cache_size;
 	unsigned int threshold;
 	int ret;
 
+	resctrl_rmid_realloc_limit = boot_cpu_data.x86_cache_size * 1024;
 	hw_res->mon_scale = boot_cpu_data.x86_cache_occ_scale;
 	r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1;
 	hw_res->mbm_width = MBM_CNTR_WIDTH_BASE;
@@ -764,7 +769,7 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
 	 *
 	 * For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC.
 	 */
-	threshold = cl_size * 1024 / r->num_rmid;
+	threshold = resctrl_rmid_realloc_limit / r->num_rmid;
 
 	/*
 	 * Because num_rmid may not be a power of two, round the value
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 7c35561e5216..0e9f9a527e6a 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1059,7 +1059,7 @@ static ssize_t max_threshold_occ_write(struct kernfs_open_file *of,
 	if (ret)
 		return ret;
 
-	if (bytes > (boot_cpu_data.x86_cache_size * 1024))
+	if (bytes > resctrl_rmid_realloc_limit)
 		return -EINVAL;
 
 	resctrl_rmid_realloc_threshold = bytes;
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index fc4805901f1a..9c360999fb9b 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -251,5 +251,6 @@ void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
 			     u32 rmid, enum resctrl_event_id eventid);
 
 extern unsigned int resctrl_rmid_realloc_threshold;
+extern unsigned int resctrl_rmid_realloc_limit;
 
 #endif /* _RESCTRL_H */
-- 
2.30.2