Fix a CPU topology parsing bug on AMD guests, and address

a lockdep warning on the resctrl filesystem.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-urgent-2025-09-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
 "Fix a CPU topology parsing bug on AMD guests, and address
  a lockdep warning in the resctrl filesystem"

* tag 'x86-urgent-2025-09-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  fs/resctrl: Eliminate false positive lockdep warning when reading SNC counters
  x86/cpu/topology: Always try cpu_parse_topology_ext() on AMD/Hygon

arch/x86/kernel/cpu/topology_amd.c

@@ -175,27 +175,30 @@ static void topoext_fixup(struct topo_scan *tscan)
 
 static void parse_topology_amd(struct topo_scan *tscan)
 {
-	bool has_topoext = false;
-
 	/*
-	 * If the extended topology leaf 0x8000_001e is available
+	 * Try to get SMT, CORE, TILE, and DIE shifts from extended
-	 * try to get SMT, CORE, TILE, and DIE shifts from extended
 	 * CPUID leaf 0x8000_0026 on supported processors first. If
 	 * extended CPUID leaf 0x8000_0026 is not supported, try to
-	 * get SMT and CORE shift from leaf 0xb first, then try to
+	 * get SMT and CORE shift from leaf 0xb. If either leaf is
-	 * get the CORE shift from leaf 0x8000_0008.
+	 * available, cpu_parse_topology_ext() will return true.
 	 */
-	if (cpu_feature_enabled(X86_FEATURE_TOPOEXT))
+	bool has_xtopology = cpu_parse_topology_ext(tscan);
-		has_topoext = cpu_parse_topology_ext(tscan);
 
 	if (cpu_feature_enabled(X86_FEATURE_AMD_HTR_CORES))
 		tscan->c->topo.cpu_type = cpuid_ebx(0x80000026);
 
-	if (!has_topoext && !parse_8000_0008(tscan))
+	/*
+	 * If XTOPOLOGY leaves (0x26/0xb) are not available, try to
+	 * get the CORE shift from leaf 0x8000_0008 first.
+	 */
+	if (!has_xtopology && !parse_8000_0008(tscan))
 		return;
 
-	/* Prefer leaf 0x8000001e if available */
+	/*
-	if (parse_8000_001e(tscan, has_topoext))
+	 * Prefer leaf 0x8000001e if available to get the SMT shift and
+	 * the initial APIC ID if XTOPOLOGY leaves are not available.
+	 */
+	if (parse_8000_001e(tscan, has_xtopology))
 		return;
 
 	/* Try the NODEID MSR */

fs/resctrl/ctrlmondata.c

@@ -625,11 +625,11 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
 		 */
 		list_for_each_entry(d, &r->mon_domains, hdr.list) {
 			if (d->ci_id == domid) {
-				rr.ci_id = d->ci_id;
 				cpu = cpumask_any(&d->hdr.cpu_mask);
 				ci = get_cpu_cacheinfo_level(cpu, RESCTRL_L3_CACHE);
 				if (!ci)
 					continue;
+				rr.ci = ci;
 				mon_event_read(&rr, r, NULL, rdtgrp,
 					       &ci->shared_cpu_map, evtid, false);
 				goto checkresult;

fs/resctrl/internal.h

@@ -98,7 +98,7 @@ struct mon_data {
  *	   domains in @r sharing L3 @ci.id
  * @evtid: Which monitor event to read.
  * @first: Initialize MBM counter when true.
- * @ci_id: Cacheinfo id for L3. Only set when @d is NULL. Used when summing domains.
+ * @ci:    Cacheinfo for L3. Only set when @d is NULL. Used when summing domains.
  * @err:   Error encountered when reading counter.
  * @val:   Returned value of event counter. If @rgrp is a parent resource group,
  *	   @val includes the sum of event counts from its child resource groups.
@@ -112,7 +112,7 @@ struct rmid_read {
 	struct rdt_mon_domain	*d;
 	enum resctrl_event_id	evtid;
 	bool			first;
-	unsigned int		ci_id;
+	struct cacheinfo	*ci;
 	int			err;
 	u64			val;
 	void			*arch_mon_ctx;

fs/resctrl/monitor.c

@@ -361,7 +361,6 @@ static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
 {
 	int cpu = smp_processor_id();
 	struct rdt_mon_domain *d;
-	struct cacheinfo *ci;
 	struct mbm_state *m;
 	int err, ret;
 	u64 tval = 0;
@@ -389,8 +388,7 @@ static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
 	}
 
 	/* Summing domains that share a cache, must be on a CPU for that cache. */
-	ci = get_cpu_cacheinfo_level(cpu, RESCTRL_L3_CACHE);
+	if (!cpumask_test_cpu(cpu, &rr->ci->shared_cpu_map))
-	if (!ci || ci->id != rr->ci_id)
 		return -EINVAL;
 
 	/*
@@ -402,7 +400,7 @@ static int __mon_event_count(u32 closid, u32 rmid, struct rmid_read *rr)
 	 */
 	ret = -EINVAL;
 	list_for_each_entry(d, &rr->r->mon_domains, hdr.list) {
-		if (d->ci_id != rr->ci_id)
+		if (d->ci_id != rr->ci->id)
 			continue;
 		err = resctrl_arch_rmid_read(rr->r, d, closid, rmid,
 					     rr->evtid, &tval, rr->arch_mon_ctx);