From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] x86/cpu: Use cpu_feature_enabled() when checking global pages support
Date: Wed, 25 Jan 2023 08:50:13 +0100 [thread overview]
Message-ID: <20230125075013.9292-1-bp@alien8.de> (raw)
From: "Borislav Petkov (AMD)" <bp@alien8.de>
X86_FEATURE_PGE determines whether the CPU has enabled global page
translations support. Use the faster cpu_feature_enabled() check to
shave off some more cycles when flushing all TLB entries, including the
global ones.
What this practically saves is:
mov 0x82eb308(%rip),%rax # 0xffffffff8935bec8 <boot_cpu_data+40>
test $0x20,%ah
which test the bit. Not a lot but TLB flushing is a timing-sensitive
path so anything to make it even faster.
No functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
arch/x86/mm/tlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index c1e31e9a85d7..92d73ccede70 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -1205,7 +1205,7 @@ void __flush_tlb_all(void)
*/
VM_WARN_ON_ONCE(preemptible());
- if (boot_cpu_has(X86_FEATURE_PGE)) {
+ if (cpu_feature_enabled(X86_FEATURE_PGE)) {
__flush_tlb_global();
} else {
/*
--
2.35.1
next reply other threads:[~2023-01-25 7:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 7:50 Borislav Petkov [this message]
2023-01-25 9:43 ` [tip: x86/mm] x86/cpu: Use cpu_feature_enabled() when checking global pages support tip-bot2 for Borislav Petkov (AMD)
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