linux-kernel - [PATCH v12 07/16] x86/mm: use INVLPGB in flush_tlb

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Message-ID: <20250221005345.2156760-8-riel@surriel.com>
Date: Thu, 20 Feb 2025 19:53:06 -0500
From: Rik van Riel <riel@...riel.com>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	bp@...en8.de,
	peterz@...radead.org,
	dave.hansen@...ux.intel.com,
	zhengqi.arch@...edance.com,
	nadav.amit@...il.com,
	thomas.lendacky@....com,
	kernel-team@...a.com,
	linux-mm@...ck.org,
	akpm@...ux-foundation.org,
	jackmanb@...gle.com,
	jannh@...gle.com,
	mhklinux@...look.com,
	andrew.cooper3@...rix.com,
	Manali.Shukla@....com,
	Rik van Riel <riel@...riel.com>
Subject: [PATCH v12 07/16] x86/mm: use INVLPGB in flush_tlb_all

The flush_tlb_all() function is not used a whole lot, but we might
as well use broadcast TLB flushing there, too.

Signed-off-by: Rik van Riel <riel@...riel.com>
Tested-by: Manali Shukla <Manali.Shukla@....com>
Tested-by: Brendan Jackman <jackmanb@...gle.com>
Tested-by: Michael Kelley <mhklinux@...look.com>
---
 arch/x86/mm/tlb.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 59396a3c6e9c..2d7ed0fda61f 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -1065,6 +1065,16 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 }
 
 
+static bool broadcast_flush_tlb_all(void)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		return false;
+
+	guard(preempt)();
+	invlpgb_flush_all();
+	return true;
+}
+
 static void do_flush_tlb_all(void *info)
 {
 	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
@@ -1074,6 +1084,12 @@ static void do_flush_tlb_all(void *info)
 void flush_tlb_all(void)
 {
 	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
+
+	/* First try (faster) hardware-assisted TLB invalidation. */
+	if (broadcast_flush_tlb_all())
+		return;
+
+	/* Fall back to the IPI-based invalidation. */
 	on_each_cpu(do_flush_tlb_all, NULL, 1);
 }
 
-- 
2.47.1