linux-kernel - [PATCH v4 14/21] arm64: Honor VHE being disabled from the command-line

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Date:   Mon, 18 Jan 2021 09:45:26 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        David Brazdil <dbrazdil@...gle.com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Ajay Patil <pajay@....qualcomm.com>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        Srinivas Ramana <sramana@...eaurora.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kernel-team@...roid.com
Subject: [PATCH v4 14/21] arm64: Honor VHE being disabled from the command-line

Finally we can check whether VHE is disabled on the command line,
and not enable it if that's the user's wish.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kernel/hyp-stub.S | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index 59820f9b8522..bbab2148a2a2 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -77,13 +77,24 @@ SYM_CODE_END(el1_sync)
 SYM_CODE_START_LOCAL(mutate_to_vhe)
 	// Sanity check: MMU *must* be off
 	mrs	x0, sctlr_el2
-	tbnz	x0, #0, 1f
+	tbnz	x0, #0, 2f
 
 	// Needs to be VHE capable, obviously
 	mrs	x0, id_aa64mmfr1_el1
 	ubfx	x0, x0, #ID_AA64MMFR1_VHE_SHIFT, #4
-	cbz	x0, 1f
+	cbz	x0, 2f
 
+	// Check whether VHE is disabled from the command line
+	adr_l	x1, id_aa64mmfr1_val
+	ldr	x0, [x1]
+	adr_l	x1, id_aa64mmfr1_mask
+	ldr	x1, [x1]
+	ubfx	x0, x0, #ID_AA64MMFR1_VHE_SHIFT, #4
+	ubfx	x1, x1, #ID_AA64MMFR1_VHE_SHIFT, #4
+	cbz	x1, 1f
+	and	x0, x0, x1
+	cbz	x0, 2f
+1:
 	// Engage the VHE magic!
 	mov_q	x0, HCR_HOST_VHE_FLAGS
 	msr	hcr_el2, x0
@@ -152,7 +163,7 @@ skip_spe:
 	orr	x0, x0, x1
 	msr	spsr_el1, x0
 
-1:	eret
+2:	eret
 SYM_CODE_END(mutate_to_vhe)
 
 .macro invalid_vector	label
-- 
2.29.2