Commit 05d48035 authored by Ahmed S. Darwish's avatar Ahmed S. Darwish Committed by Ingo Molnar
Browse files

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: default avatarAhmed S. Darwish <darwi@linutronix.de>
Signed-off-by: default avatarIngo 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
parent fda5f817

arch/x86/kernel/cpu/cacheinfo.c

+13 −11
Original line number Diff line number Diff line
@@ -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)