[PATCH v6 18/34] arm_mpam: Reset MSC controls from cpuhp callbacks

[Ben Horgan]

From: James Morse <james.morse at arm.com>

When a CPU comes online, it may bring a newly accessible MSC with
it. Only the default partid has its value reset by hardware, and
even then the MSC might not have been reset since its config was
previously dirtied. e.g. Kexec.

Any in-use partid must have its configuration restored, or reset.
In-use partids may be held in caches and evicted later.

MSC are also reset when CPUs are taken offline to cover cases where
firmware doesn't reset the MSC over reboot using UEFI, or kexec
where there is no firmware involvement.

If the configuration for a RIS has not been touched since it was
brought online, it does not need resetting again.

To reset, write the maximum values for all discovered controls.

CC: Rohit Mathew <Rohit.Mathew at arm.com>
Signed-off-by: James Morse <james.morse at arm.com>
Reviewed-by: Fenghua Yu <fenghuay at nvidia.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron at huawei.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng at jp.fujitsu.com>
Reviewed-by: Gavin Shan <gshan at redhat.com>
Tested-by: Fenghua Yu <fenghuay at nvidia.com>
Tested-by: Shaopeng Tan <tan.shaopeng at jp.fujitsu.com>
Tested-by: Peter Newman <peternewman at google.com>
Tested-by: Carl Worth <carl at os.amperecomputing.com>
Tested-by: Gavin Shan <gshan at redhat.com>
Tested-by: Zeng Heng <zengheng4 at huawei.com>
Tested-by: Hanjun Guo <guohanjun at huawei.com>
Signed-off-by: Ben Horgan <ben.horgan at arm.com>
---
Changes since v3:
Add tags - thanks!
---
 drivers/resctrl/mpam_devices.c  | 109 ++++++++++++++++++++++++++++++++
 drivers/resctrl/mpam_internal.h |   3 +
 2 files changed, 112 insertions(+)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index f9ac88bf06b7..4bd4d57a3baa 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -7,6 +7,7 @@
 #include <linux/atomic.h>
 #include <linux/arm_mpam.h>
 #include <linux/bitfield.h>
+#include <linux/bitmap.h>
 #include <linux/cacheinfo.h>
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
@@ -752,8 +753,104 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
 	return 0;
 }
 
+static void mpam_reset_msc_bitmap(struct mpam_msc *msc, u16 reg, u16 wd)
+{
+	u32 num_words, msb;
+	u32 bm = ~0;
+	int i;
+
+	lockdep_assert_held(&msc->part_sel_lock);
+
+	if (wd == 0)
+		return;
+
+	/*
+	 * Write all ~0 to all but the last 32bit-word, which may
+	 * have fewer bits...
+	 */
+	num_words = DIV_ROUND_UP(wd, 32);
+	for (i = 0; i < num_words - 1; i++, reg += sizeof(bm))
+		__mpam_write_reg(msc, reg, bm);
+
+	/*
+	 * ....and then the last (maybe) partial 32bit word. When wd is a
+	 * multiple of 32, msb should be 31 to write a full 32bit word.
+	 */
+	msb = (wd - 1) % 32;
+	bm = GENMASK(msb, 0);
+	__mpam_write_reg(msc, reg, bm);
+}
+
+static void mpam_reset_ris_partid(struct mpam_msc_ris *ris, u16 partid)
+{
+	struct mpam_msc *msc = ris->vmsc->msc;
+	struct mpam_props *rprops = &ris->props;
+
+	WARN_ON_ONCE(!srcu_read_lock_held((&mpam_srcu)));
+
+	mutex_lock(&msc->part_sel_lock);
+	__mpam_part_sel(ris->ris_idx, partid, msc);
+
+	if (mpam_has_feature(mpam_feat_cpor_part, rprops))
+		mpam_reset_msc_bitmap(msc, MPAMCFG_CPBM, rprops->cpbm_wd);
+
+	if (mpam_has_feature(mpam_feat_mbw_part, rprops))
+		mpam_reset_msc_bitmap(msc, MPAMCFG_MBW_PBM, rprops->mbw_pbm_bits);
+
+	if (mpam_has_feature(mpam_feat_mbw_min, rprops))
+		mpam_write_partsel_reg(msc, MBW_MIN, 0);
+
+	if (mpam_has_feature(mpam_feat_mbw_max, rprops))
+		mpam_write_partsel_reg(msc, MBW_MAX, MPAMCFG_MBW_MAX_MAX);
+
+	mutex_unlock(&msc->part_sel_lock);
+}
+
+static void mpam_reset_ris(struct mpam_msc_ris *ris)
+{
+	u16 partid, partid_max;
+
+	WARN_ON_ONCE(!srcu_read_lock_held((&mpam_srcu)));
+
+	if (ris->in_reset_state)
+		return;
+
+	spin_lock(&partid_max_lock);
+	partid_max = mpam_partid_max;
+	spin_unlock(&partid_max_lock);
+	for (partid = 0; partid <= partid_max; partid++)
+		mpam_reset_ris_partid(ris, partid);
+}
+
+static void mpam_reset_msc(struct mpam_msc *msc, bool online)
+{
+	struct mpam_msc_ris *ris;
+
+	list_for_each_entry_srcu(ris, &msc->ris, msc_list, srcu_read_lock_held(&mpam_srcu)) {
+		mpam_reset_ris(ris);
+
+		/*
+		 * Set in_reset_state when coming online. The reset state
+		 * for non-zero partid may be lost while the CPUs are offline.
+		 */
+		ris->in_reset_state = online;
+	}
+}
+
 static int mpam_cpu_online(unsigned int cpu)
 {
+	struct mpam_msc *msc;
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(msc, &mpam_all_msc, all_msc_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (!cpumask_test_cpu(cpu, &msc->accessibility))
+			continue;
+
+		if (atomic_fetch_inc(&msc->online_refs) == 0)
+			mpam_reset_msc(msc, true);
+	}
+
 	return 0;
 }
 
@@ -792,6 +889,18 @@ static int mpam_discovery_cpu_online(unsigned int cpu)
 
 static int mpam_cpu_offline(unsigned int cpu)
 {
+	struct mpam_msc *msc;
+
+	guard(srcu)(&mpam_srcu);
+	list_for_each_entry_srcu(msc, &mpam_all_msc, all_msc_list,
+				 srcu_read_lock_held(&mpam_srcu)) {
+		if (!cpumask_test_cpu(cpu, &msc->accessibility))
+			continue;
+
+		if (atomic_dec_and_test(&msc->online_refs))
+			mpam_reset_msc(msc, false);
+	}
+
 	return 0;
 }
 
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
index 4749ac223adc..dec485cd8a91 100644
--- a/drivers/resctrl/mpam_internal.h
+++ b/drivers/resctrl/mpam_internal.h
@@ -5,6 +5,7 @@
 #define MPAM_INTERNAL_H
 
 #include <linux/arm_mpam.h>
+#include <linux/atomic.h>
 #include <linux/bitmap.h>
 #include <linux/cpumask.h>
 #include <linux/io.h>
@@ -45,6 +46,7 @@ struct mpam_msc {
 	enum mpam_msc_iface	iface;
 	u32			nrdy_usec;
 	cpumask_t		accessibility;
+	atomic_t		online_refs;
 
 	/*
 	 * probe_lock is only taken during discovery. After discovery these
@@ -198,6 +200,7 @@ struct mpam_msc_ris {
 	u8			ris_idx;
 	u64			idr;
 	struct mpam_props	props;
+	bool			in_reset_state;
 
 	cpumask_t		affinity;
 
-- 
2.43.0