[PATCH 5.11 558/775] arm64: Add missing ISB after invalidating TLB in __primary_switch

[Greg Kroah-Hartman]

From: Marc Zyngier <maz@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Link: https://lore.kernel.org/r/20210224093738.3629662-3-maz@xxxxxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 a0dc987724eda..7ec430e18f95e 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -882,6 +882,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
 
 	tlbi	vmalle1				// Remove any stale TLB entries
 	dsb	nsh
+	isb
 
 	msr	sctlr_el1, x19			// re-enable the MMU
 	isb
-- 
2.27.0