linux-kernel - [PATCH 4.9 086/134] arm64: Add missing ISB after invalidating TLB in __primary

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Message-Id: <20210301161017.804816014@linuxfoundation.org>
Date:   Mon,  1 Mar 2021 17:13:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Will Deacon <will@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 086/134] arm64: Add missing ISB after invalidating TLB in __primary_switch

From: Marc Zyngier <maz@...nel.org>

[ Upstream commit 9d41053e8dc115c92b8002c3db5f545d7602498b ]

Although there has been a bit of back and forth on the subject, it
appears that invalidating TLBs requires an ISB instruction when FEAT_ETS
is not implemented by the CPU.

>>From the bible:

  | In an implementation that does not implement FEAT_ETS, a TLB
  | maintenance instruction executed by a PE, PEx, can complete at any
  | time after it is issued, but is only guaranteed to be finished for a
  | PE, PEx, after the execution of DSB by the PEx followed by a Context
  | synchronization event

Add the missing ISB in __primary_switch, just in case.

Fixes: 3c5e9f238bc4 ("arm64: head.S: move KASLR processing out of __enable_mmu()")
Suggested-by: Will Deacon <will@...nel.org>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Acked-by: Mark Rutland <mark.rutland@....com>
Link: https://lore.kernel.org/r/20210224093738.3629662-3-maz@kernel.org
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kernel/head.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index aba534959377b..3875423836622 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -846,6 +846,7 @@ __primary_switch:
 
 	tlbi	vmalle1				// Remove any stale TLB entries
 	dsb	nsh
+	isb
 
 	msr	sctlr_el1, x19			// re-enable the MMU
 	isb
-- 
2.27.0