From: Ahmed S. Darwish <darwi@linutronix.de>
Date: Mon, 24 Mar 2025 13:33:21 +0000 (+0100)
Subject: x86/cacheinfo: Extract out cache self-snoop checks
X-Git-Tag: v6.16-rc1~195^2~29^2~24
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=05d48035e5f69cfe3c125b2bac47e4003b4acccf;p=thirdparty%2Fkernel%2Flinux.git

x86/cacheinfo: Extract out cache self-snoop checks

The logic of not doing a cache flush if the CPU declares cache self
snooping support is repeated across the x86/cacheinfo code.  Extract it
into its own function.

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/20250324133324.23458-27-darwi@linutronix.de
---

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 7b274da7c725b..231470cdc1da0 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -646,6 +646,17 @@ int populate_cache_leaves(unsigned int cpu)
 static unsigned long saved_cr4;
 static DEFINE_RAW_SPINLOCK(cache_disable_lock);
 
+/*
+ * Cache flushing is the most time-consuming step when programming the
+ * MTRRs.  On many Intel CPUs without known erratas, it can be skipped
+ * if the CPU declares cache self-snooping support.
+ */
+static void maybe_flush_caches(void)
+{
+	if (!static_cpu_has(X86_FEATURE_SELFSNOOP))
+		wbinvd();
+}
+
 void cache_disable(void) __acquires(cache_disable_lock)
 {
 	unsigned long cr0;
@@ -663,14 +674,7 @@ void cache_disable(void) __acquires(cache_disable_lock)
 	cr0 = read_cr0() | X86_CR0_CD;
 	write_cr0(cr0);
 
-	/*
-	 * Cache flushing is the most time-consuming step when programming
-	 * the MTRRs. Fortunately, as per the Intel Software Development
-	 * Manual, we can skip it if the processor supports cache self-
-	 * snooping.
-	 */
-	if (!static_cpu_has(X86_FEATURE_SELFSNOOP))
-		wbinvd();
+	maybe_flush_caches();
 
 	/* Save value of CR4 and clear Page Global Enable (bit 7) */
 	if (cpu_feature_enabled(X86_FEATURE_PGE)) {
@@ -685,9 +689,7 @@ void cache_disable(void) __acquires(cache_disable_lock)
 	if (cpu_feature_enabled(X86_FEATURE_MTRR))
 		mtrr_disable();
 
-	/* Again, only flush caches if we have to. */
-	if (!static_cpu_has(X86_FEATURE_SELFSNOOP))
-		wbinvd();
+	maybe_flush_caches();
 }
 
 void cache_enable(void) __releases(cache_disable_lock)