linux-kernel - [PATCH v2 01/10] um: Stop tracking virtual CPUs via mm

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Message-Id: <20250810055136.897712-2-tiwei.bie@linux.dev>
Date: Sun, 10 Aug 2025 13:51:27 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: richard@....at,
	anton.ivanov@...bridgegreys.com,
	johannes@...solutions.net
Cc: linux-um@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	benjamin@...solutions.net,
	arnd@...db.de,
	tiwei.btw@...group.com,
	tiwei.bie@...ux.dev
Subject: [PATCH v2 01/10] um: Stop tracking virtual CPUs via mm_cpumask()

From: Tiwei Bie <tiwei.btw@...group.com>

In UML, each user address space is represented as a separate stub
process on the host. Therefore, user address spaces do not require
TLB management on UML virtual CPUs, and it's unnecessary to track
which virtual CPUs they have executed on.

Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>
---
 arch/um/include/asm/mmu_context.h | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/arch/um/include/asm/mmu_context.h b/arch/um/include/asm/mmu_context.h
index 0bbb24868557..c727e56ba116 100644
--- a/arch/um/include/asm/mmu_context.h
+++ b/arch/um/include/asm/mmu_context.h
@@ -13,20 +13,9 @@
 #include <asm/mm_hooks.h>
 #include <asm/mmu.h>
 
-#define activate_mm activate_mm
-static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
-{
-}
-
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, 
 			     struct task_struct *tsk)
 {
-	unsigned cpu = smp_processor_id();
-
-	if (prev != next) {
-		cpumask_clear_cpu(cpu, mm_cpumask(prev));
-		cpumask_set_cpu(cpu, mm_cpumask(next));
-	}
 }
 
 #define init_new_context init_new_context
-- 
2.34.1