linux-kernel - [PATCH 4.9 13/21] arm64: reduce el2

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Message-Id: <20220110071813.246928726@linuxfoundation.org>
Date:   Mon, 10 Jan 2022 08:23:00 +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, Marc Zyngier <marc.zyngier@....com>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH 4.9 13/21] arm64: reduce el2_setup branching

From: Mark Rutland <mark.rutland@....com>

commit 3ad47d055aa88d9f4189253f5b5c485f4c4626b2 upstream.

The early el2_setup code is a little convoluted, with two branches where
one would do. This makes the code more painful to read than is
necessary.

We can remove a branch and simplify the logic by moving the early return
in the booted-at-EL1 case earlier in the function. This separates it
from all the setup logic that only makes sense for EL2.

Acked-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Will Deacon <will.deacon@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/kernel/head.S |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -489,13 +489,8 @@ ENTRY(el2_setup)
 	msr	SPsel, #1			// We want to use SP_EL{1,2}
 	mrs	x0, CurrentEL
 	cmp	x0, #CurrentEL_EL2
-	b.ne	1f
-	mrs	x0, sctlr_el2
-CPU_BE(	orr	x0, x0, #(1 << 25)	)	// Set the EE bit for EL2
-CPU_LE(	bic	x0, x0, #(1 << 25)	)	// Clear the EE bit for EL2
-	msr	sctlr_el2, x0
-	b	2f
-1:	mrs	x0, sctlr_el1
+	b.eq	1f
+	mrs	x0, sctlr_el1
 CPU_BE(	orr	x0, x0, #(3 << 24)	)	// Set the EE and E0E bits for EL1
 CPU_LE(	bic	x0, x0, #(3 << 24)	)	// Clear the EE and E0E bits for EL1
 	msr	sctlr_el1, x0
@@ -503,7 +498,11 @@ CPU_LE(	bic	x0, x0, #(3 << 24)	)	// Clea
 	isb
 	ret
 
-2:
+1:	mrs	x0, sctlr_el2
+CPU_BE(	orr	x0, x0, #(1 << 25)	)	// Set the EE bit for EL2
+CPU_LE(	bic	x0, x0, #(1 << 25)	)	// Clear the EE bit for EL2
+	msr	sctlr_el2, x0
+
 #ifdef CONFIG_ARM64_VHE
 	/*
 	 * Check for VHE being present. For the rest of the EL2 setup,