linux-kernel - [tip: x86/mm] x86/mm: Consolidate full flush threshold decision

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Message-ID: <174121058815.14745.1995524860475217029.tip-bot2@tip-bot2>
Date: Wed, 05 Mar 2025 21:36:28 -0000
From: "tip-bot2 for Rik van Riel" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Dave Hansen <dave.hansen@...el.com>, Rik van Riel <riel@...riel.com>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/mm] x86/mm: Consolidate full flush threshold decision

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     fd521566cc0cd5e327683fea70cba93b1966ebac
Gitweb:        https://git.kernel.org/tip/fd521566cc0cd5e327683fea70cba93b1966ebac
Author:        Rik van Riel <riel@...riel.com>
AuthorDate:    Tue, 25 Feb 2025 22:00:36 -05:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Tue, 04 Mar 2025 11:39:38 +01:00

x86/mm: Consolidate full flush threshold decision

Reduce code duplication by consolidating the decision point for whether to do
individual invalidations or a full flush inside get_flush_tlb_info().

Suggested-by: Dave Hansen <dave.hansen@...el.com>
Signed-off-by: Rik van Riel <riel@...riel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
Acked-by: Dave Hansen <dave.hansen@...el.com>
Link: https://lore.kernel.org/r/20250226030129.530345-2-riel@surriel.com
---
 arch/x86/mm/tlb.c | 41 +++++++++++++++++++----------------------
 1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index ffc25b3..dbcb5c9 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -1000,6 +1000,15 @@ static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
 	BUG_ON(this_cpu_inc_return(flush_tlb_info_idx) != 1);
 #endif
 
+	/*
+	 * If the number of flushes is so large that a full flush
+	 * would be faster, do a full flush.
+	 */
+	if ((end - start) >> stride_shift > tlb_single_page_flush_ceiling) {
+		start = 0;
+		end = TLB_FLUSH_ALL;
+	}
+
 	info->start		= start;
 	info->end		= end;
 	info->mm		= mm;
@@ -1026,17 +1035,8 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 				bool freed_tables)
 {
 	struct flush_tlb_info *info;
+	int cpu = get_cpu();
 	u64 new_tlb_gen;
-	int cpu;
-
-	cpu = get_cpu();
-
-	/* Should we flush just the requested range? */
-	if ((end == TLB_FLUSH_ALL) ||
-	    ((end - start) >> stride_shift) > tlb_single_page_flush_ceiling) {
-		start = 0;
-		end = TLB_FLUSH_ALL;
-	}
 
 	/* This is also a barrier that synchronizes with switch_mm(). */
 	new_tlb_gen = inc_mm_tlb_gen(mm);
@@ -1089,22 +1089,19 @@ static void do_kernel_range_flush(void *info)
 
 void flush_tlb_kernel_range(unsigned long start, unsigned long end)
 {
-	/* Balance as user space task's flush, a bit conservative */
-	if (end == TLB_FLUSH_ALL ||
-	    (end - start) > tlb_single_page_flush_ceiling << PAGE_SHIFT) {
-		on_each_cpu(do_flush_tlb_all, NULL, 1);
-	} else {
-		struct flush_tlb_info *info;
+	struct flush_tlb_info *info;
+
+	guard(preempt)();
 
-		preempt_disable();
-		info = get_flush_tlb_info(NULL, start, end, 0, false,
-					  TLB_GENERATION_INVALID);
+	info = get_flush_tlb_info(NULL, start, end, PAGE_SHIFT, false,
+				  TLB_GENERATION_INVALID);
 
+	if (info->end == TLB_FLUSH_ALL)
+		on_each_cpu(do_flush_tlb_all, NULL, 1);
+	else
 		on_each_cpu(do_kernel_range_flush, info, 1);
 
-		put_flush_tlb_info();
-		preempt_enable();
-	}
+	put_flush_tlb_info();
 }
 
 /*