[kvm-unit-tests PATCH 5/6] arm64: Configure SCTLR_EL1 at boot

From: Alexandru Elisei <alexandru.elisei@arm.com>
To: drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Subject: [kvm-unit-tests PATCH 5/6] arm64: Configure SCTLR_EL1 at boot
Date: Sat, 27 Feb 2021 10:42:00 +0000	[thread overview]
Message-ID: <20210227104201.14403-6-alexandru.elisei@arm.com> (raw)
In-Reply-To: <20210227104201.14403-1-alexandru.elisei@arm.com>

Some fields in SCTLR_EL1 are UNKNOWN at reset and the arm64 boot
requirements, as stated by Linux in Documentation/arm64/booting.rst, do not
specify a particular value for all the fields. Do not rely on the good will
of the hypervisor and userspace to set SCTLR_EL1 to a sane value (by their
definition of sane) and set SCTLR_EL1 explicitely before running setup().
This will ensure that all tests are performed with the hardware set up
identically, regardless of the KVM or VMM versions.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
 lib/arm64/asm/sysreg.h | 7 +++++++
 arm/cstart64.S         | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/lib/arm64/asm/sysreg.h b/lib/arm64/asm/sysreg.h
index 9d6b4fc66936..18c4ed39557a 100644
--- a/lib/arm64/asm/sysreg.h
+++ b/lib/arm64/asm/sysreg.h
@@ -8,6 +8,8 @@
 #ifndef _ASMARM64_SYSREG_H_
 #define _ASMARM64_SYSREG_H_
 
+#include <linux/const.h>
+
 #define sys_reg(op0, op1, crn, crm, op2) \
 	((((op0)&3)<<19)|((op1)<<16)|((crn)<<12)|((crm)<<8)|((op2)<<5))
 
@@ -87,4 +89,9 @@ asm(
 #define SCTLR_EL1_A	(1 << 1)
 #define SCTLR_EL1_M	(1 << 0)
 
+#define SCTLR_EL1_RES1	(_BITUL(7) | _BITUL(8) | _BITUL(11) | _BITUL(20) | \
+			 _BITUL(22) | _BITUL(23) | _BITUL(28) | _BITUL(29))
+#define INIT_SCTLR_EL1_MMU_OFF	\
+			SCTLR_EL1_RES1
+
 #endif /* _ASMARM64_SYSREG_H_ */
diff --git a/arm/cstart64.S b/arm/cstart64.S
index f6c5d2ebccf3..42a838ff4c38 100644
--- a/arm/cstart64.S
+++ b/arm/cstart64.S
@@ -52,6 +52,11 @@ start:
 	b	1b
 
 1:
+	/* set SCTLR_EL1 to a known value */
+	ldr	x4, =INIT_SCTLR_EL1_MMU_OFF
+	msr	sctlr_el1, x4
+	isb
+
 	/* set up stack */
 	mov	x4, #1
 	msr	spsel, x4
-- 
2.30.1

