linux-kernel - [PATCH v16 21/34] x86/resctrl: Refactor resctrl_arch_rmid

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Message-ID: <451c774e1865d53664f5eac612570f753679024d.1753467772.git.babu.moger@amd.com>
Date: Fri, 25 Jul 2025 13:29:40 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <tony.luck@...el.com>, <reinette.chatre@...el.com>,
	<james.morse@....com>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <x86@...nel.org>, <hpa@...or.com>,
	<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
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	<fvdl@...gle.com>, <seanjc@...gle.com>, <jpoimboe@...nel.org>,
	<pawan.kumar.gupta@...ux.intel.com>, <xin@...or.com>,
	<manali.shukla@....com>, <babu.moger@....com>, <tao1.su@...ux.intel.com>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>
Subject: [PATCH v16 21/34] x86/resctrl: Refactor resctrl_arch_rmid_read()

resctrl_arch_rmid_read() adjusts the value obtained from MSR_IA32_QM_CTR to
account for the overflow for MBM events and apply counter scaling for all
the events. This logic is common to both reading an RMID and reading a
hardware counter directly.

Refactor the hardware value adjustment logic into get_corrected_val() to
prepare for support of reading a hardware counter.

Signed-off-by: Babu Moger <babu.moger@....com>
---
v16: Rephrased the changelog.
     Fixed allignment.
     Renamed mbm_corrected_val() -> get_corrected_val().

v15: New patch to add arch calls resctrl_arch_cntr_read() and resctrl_arch_reset_cntr()
     with mbm_event mode.
     https://lore.kernel.org/lkml/b4b14670-9cb0-4f65-abd5-39db996e8da9@intel.com/
---
 arch/x86/kernel/cpu/resctrl/monitor.c | 38 ++++++++++++++++-----------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index ed295a6c5e66..1f77fd58e707 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -217,24 +217,13 @@ static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr, unsigned int width)
 	return chunks >> shift;
 }
 
-int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
-			   u32 unused, u32 rmid, enum resctrl_event_id eventid,
-			   u64 *val, void *ignored)
+static u64 get_corrected_val(struct rdt_resource *r, struct rdt_mon_domain *d,
+			     u32 rmid, enum resctrl_event_id eventid, u64 msr_val)
 {
 	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
 	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
-	int cpu = cpumask_any(&d->hdr.cpu_mask);
 	struct arch_mbm_state *am;
-	u64 msr_val, chunks;
-	u32 prmid;
-	int ret;
-
-	resctrl_arch_rmid_read_context_check();
-
-	prmid = logical_rmid_to_physical_rmid(cpu, rmid);
-	ret = __rmid_read_phys(prmid, eventid, &msr_val);
-	if (ret)
-		return ret;
+	u64 chunks;
 
 	am = get_arch_mbm_state(hw_dom, rmid, eventid);
 	if (am) {
@@ -246,7 +235,26 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
 		chunks = msr_val;
 	}
 
-	*val = chunks * hw_res->mon_scale;
+	return chunks * hw_res->mon_scale;
+}
+
+int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_mon_domain *d,
+			   u32 unused, u32 rmid, enum resctrl_event_id eventid,
+			   u64 *val, void *ignored)
+{
+	int cpu = cpumask_any(&d->hdr.cpu_mask);
+	u64 msr_val;
+	u32 prmid;
+	int ret;
+
+	resctrl_arch_rmid_read_context_check();
+
+	prmid = logical_rmid_to_physical_rmid(cpu, rmid);
+	ret = __rmid_read_phys(prmid, eventid, &msr_val);
+	if (ret)
+		return ret;
+
+	*val = get_corrected_val(r, d, rmid, eventid, msr_val);
 
 	return 0;
 }
-- 
2.34.1