From 5fc49d225758d1768cbaca44e5e75a0bf9c4c905 Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Sun, 21 Feb 2021 13:14:47 +0000
Subject: [PATCH] One CPUs that implement the VHE extension and have the E2H
 bit set, keep running the kernel in EL2.

ok patrick@
---
 sys/arch/arm64/arm64/locore.S       | 15 ++++++++++-----
 sys/arch/arm64/include/hypervisor.h |  3 ++-
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/sys/arch/arm64/arm64/locore.S b/sys/arch/arm64/arm64/locore.S
index 2e646b29032..d4a8b3d4cd3 100644
--- a/sys/arch/arm64/arm64/locore.S
+++ b/sys/arch/arm64/arm64/locore.S
@@ -1,4 +1,4 @@
-/* $OpenBSD: locore.S,v 1.33 2021/02/16 12:33:22 kettenis Exp $ */
+/* $OpenBSD: locore.S,v 1.34 2021/02/21 13:14:47 kettenis Exp $ */
 /*-
  * Copyright (c) 2012-2014 Andrew Turner
  * All rights reserved.
@@ -47,10 +47,15 @@ drop_to_el1:
 	mrs	x1, CurrentEL
 	lsr	x1, x1, #2
 	cmp	x1, #0x2
-	b.eq	1f
+	b.eq	2f
+1:
 	RETGUARD_CHECK(drop_to_el1, x15)
 	ret
-1:
+2:
+	/* Check for EL2 Host mode */
+	mrs	x2, hcr_el2
+	tbnz	x2, #34, 1b	/* HCR_E2H */
+
 	/* Configure the Hypervisor */
 	mov	x2, #(HCR_RW)
 	msr	hcr_el2, x2
@@ -96,13 +101,13 @@ drop_to_el1:
 	ubfx	x2, x2, #ID_AA64PFR0_GIC_SHIFT, #ID_AA64PFR0_GIC_BITS
 	/* GIC[3:0] == 0001 - GIC CPU interface via special regs. supported */
 	cmp	x2, #(ID_AA64PFR0_GIC_CPUIF_EN >> ID_AA64PFR0_GIC_SHIFT)
-	b.ne	2f
+	b.ne	3f
 
 	mrs	x2, icc_sre_el2
 	orr	x2, x2, #ICC_SRE_EL2_EN	/* Enable access from insecure EL1 */
 	orr	x2, x2, #ICC_SRE_EL2_SRE	/* Enable system registers */
 	msr	icc_sre_el2, x2
-2:
+3:
 
 	/* Set the address to return to our return address */
 	msr	elr_el2, x30
diff --git a/sys/arch/arm64/include/hypervisor.h b/sys/arch/arm64/include/hypervisor.h
index 8a7ee6ce4e3..0b91a2afc84 100644
--- a/sys/arch/arm64/include/hypervisor.h
+++ b/sys/arch/arm64/include/hypervisor.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: hypervisor.h,v 1.2 2016/12/18 14:40:25 patrick Exp $ */
+/* $OpenBSD: hypervisor.h,v 1.3 2021/02/21 13:14:47 kettenis Exp $ */
 /*-
  * Copyright (c) 2013, 2014 Andrew Turner
  * All rights reserved.
@@ -81,6 +81,7 @@
 #define	HCR_RW		0x0000000080000000
 #define	HCR_CD		0x0000000100000000
 #define	HCR_ID		0x0000000200000000
+#define	HCR_E2H		0x0000000400000000
 
 #endif
 
-- 
2.20.1