x86/cacheinfo: Separate Intel CPUID leaf 0x4 handling

init_intel_cacheinfo() was overly complex.  It parsed leaf 0x4 data,
leaf 0x2 data, and performed post-processing, all within one function.
Parent commit moved leaf 0x2 parsing and the post-processing logic into
their own functions.

Continue the refactoring by extracting leaf 0x4 parsing into its own
function.  Initialize local L2/L3 topology ID variables to BAD_APICID by
default, thus ensuring they can be used unconditionally.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250324133324.23458-25-darwi@linutronix.de

1 files changed, 54 insertions, 56 deletions

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index b39aad1ecf9c..72cc32d22c4d 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -400,73 +400,71 @@ static void intel_cacheinfo_0x2(struct cpuinfo_x86 *c)
 	intel_cacheinfo_done(c, l3, l2, l1i, l1d);
 }
 
-void init_intel_cacheinfo(struct cpuinfo_x86 *c)
+static bool intel_cacheinfo_0x4(struct cpuinfo_x86 *c)
 {
 	struct cpu_cacheinfo *ci = get_cpu_cacheinfo(c->cpu_index);
-	unsigned int l1i = 0, l1d = 0, l2 = 0, l3 = 0;
-	unsigned int l2_id = 0, l3_id = 0;
-
-	if (c->cpuid_level > 3) {
-		/*
-		 * There should be at least one leaf. A non-zero value means
-		 * that the number of leaves has been initialized.
-		 */
-		if (!ci->num_leaves)
-			ci->num_leaves = find_num_cache_leaves(c);
+	unsigned int l2_id = BAD_APICID, l3_id = BAD_APICID;
+	unsigned int l1d = 0, l1i = 0, l2 = 0, l3 = 0;
 
-		/*
-		 * Whenever possible use cpuid(4), deterministic cache
-		 * parameters cpuid leaf to find the cache details
-		 */
-		for (int i = 0; i < ci->num_leaves; i++) {
-			unsigned int num_threads_sharing, index_msb;
-			struct _cpuid4_info id4 = {};
-			int retval;
+	if (c->cpuid_level < 4)
+		return false;
 
-			retval = intel_fill_cpuid4_info(i, &id4);
-			if (retval < 0)
-				continue;
+	/*
+	 * There should be at least one leaf. A non-zero value means
+	 * that the number of leaves has been previously initialized.
+	 */
+	if (!ci->num_leaves)
+		ci->num_leaves = find_num_cache_leaves(c);
 
-			switch (id4.eax.split.level) {
-			case 1:
-				if (id4.eax.split.type == CTYPE_DATA)
-					l1d = id4.size / 1024;
-				else if (id4.eax.split.type == CTYPE_INST)
-					l1i = id4.size / 1024;
-				break;
-			case 2:
-				l2 = id4.size / 1024;
-				num_threads_sharing = 1 + id4.eax.split.num_threads_sharing;
-				index_msb = get_count_order(num_threads_sharing);
-				l2_id = c->topo.apicid & ~((1 << index_msb) - 1);
-				break;
-			case 3:
-				l3 = id4.size / 1024;
-				num_threads_sharing = 1 + id4.eax.split.num_threads_sharing;
-				index_msb = get_count_order(num_threads_sharing);
-				l3_id = c->topo.apicid & ~((1 << index_msb) - 1);
-				break;
-			default:
-				break;
-			}
+	if (!ci->num_leaves)
+		return false;
+
+	for (int i = 0; i < ci->num_leaves; i++) {
+		unsigned int num_threads_sharing, index_msb;
+		struct _cpuid4_info id4 = {};
+		int ret;
+
+		ret = intel_fill_cpuid4_info(i, &id4);
+		if (ret < 0)
+			continue;
+
+		switch (id4.eax.split.level) {
+		case 1:
+			if (id4.eax.split.type == CTYPE_DATA)
+				l1d = id4.size / 1024;
+			else if (id4.eax.split.type == CTYPE_INST)
+				l1i = id4.size / 1024;
+			break;
+		case 2:
+			l2 = id4.size / 1024;
+			num_threads_sharing = 1 + id4.eax.split.num_threads_sharing;
+			index_msb = get_count_order(num_threads_sharing);
+			l2_id = c->topo.apicid & ~((1 << index_msb) - 1);
+			break;
+		case 3:
+			l3 = id4.size / 1024;
+			num_threads_sharing = 1 + id4.eax.split.num_threads_sharing;
+			index_msb = get_count_order(num_threads_sharing);
+			l3_id = c->topo.apicid & ~((1 << index_msb) - 1);
+			break;
+		default:
+			break;
 		}
 	}
 
+	c->topo.l2c_id = l2_id;
+	c->topo.llc_id = (l3_id == BAD_APICID) ? l2_id : l3_id;
+	intel_cacheinfo_done(c, l3, l2, l1i, l1d);
+	return true;
+}
+
+void init_intel_cacheinfo(struct cpuinfo_x86 *c)
+{
 	/* Don't use CPUID(2) if CPUID(4) is supported. */
-	if (!ci->num_leaves && c->cpuid_level > 1) {
-		intel_cacheinfo_0x2(c);
+	if (intel_cacheinfo_0x4(c))
 		return;
-	}
-
-	if (l2) {
-		c->topo.llc_id = l2_id;
-		c->topo.l2c_id = l2_id;
-	}
-
-	if (l3)
-		c->topo.llc_id = l3_id;
 
-	intel_cacheinfo_done(c, l3, l2, l1i, l1d);
+	intel_cacheinfo_0x2(c);
 }
 
 static int __cache_amd_cpumap_setup(unsigned int cpu, int index,