linux-kernel - [PATCH AUTOSEL 5.9 007/147] powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE

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Date:   Mon, 26 Oct 2020 19:46:45 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 5.9 007/147] powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM

From: Nicholas Piggin <npiggin@...il.com>

[ Upstream commit 66acd46080bd9e5ad2be4b0eb1d498d5145d058e ]

powerpc uses IPIs in some situations to switch a kernel thread away
from a lazy tlb mm, which is subject to the TLB flushing race
described in the changelog introducing ARCH_WANT_IRQS_OFF_ACTIVATE_MM.

Signed-off-by: Nicholas Piggin <npiggin@...il.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20200914045219.3736466-3-npiggin@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/Kconfig                   | 1 +
 arch/powerpc/include/asm/mmu_context.h | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 787e829b6f25c..8250c0fd85285 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -148,6 +148,7 @@ config PPC
 	select ARCH_USE_QUEUED_RWLOCKS		if PPC_QUEUED_SPINLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS	if PPC_QUEUED_SPINLOCKS
 	select ARCH_WANT_IPC_PARSE_VERSION
+	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select ARCH_WEAK_RELEASE_ACQUIRE
 	select BINFMT_ELF
 	select BUILDTIME_TABLE_SORT
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 7f3658a973846..e02aa793420b8 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -244,7 +244,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
  */
 static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
-	switch_mm(prev, next, current);
+	switch_mm_irqs_off(prev, next, current);
 }
 
 /* We don't currently use enter_lazy_tlb() for anything */
-- 
2.25.1