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From f75060be04aaed4bb5a07cb40361d694b3775f4a Mon Sep 17 00:00:00 2001
From: Peter Hoyes <Peter.Hoyes@arm.com>
Date: Fri, 10 Dec 2021 16:37:26 +0000
Subject: [PATCH 5/9] armv8: Make disabling HVC configurable when switching to
EL1
On the BASER_FVP there is no EL3, so HVC is used to provide PSCI
services. Therefore we cannot disable hypercalls.
Create CONFIG_ARMV8_DISABLE_HVC (dependent on CONFIG_ARMV8_TO_EL1) to
control whether to disable HVC exceptions in HCR_EL2->HCD
Issue-Id: SCM-3728
Upstream-Status: Inappropriate [other]
Implementation pending further discussion
Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Change-Id: I463d82f1db8a3cafcab40a9c0c208753569cc300
---
arch/arm/cpu/armv8/Kconfig | 9 +++++++++
arch/arm/include/asm/macro.h | 10 ++++++++--
configs/vexpress_aemv8r_defconfig | 1 +
3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/arm/cpu/armv8/Kconfig b/arch/arm/cpu/armv8/Kconfig
index 110adf63b3..a821e219d8 100644
--- a/arch/arm/cpu/armv8/Kconfig
+++ b/arch/arm/cpu/armv8/Kconfig
@@ -199,4 +199,13 @@ config ARMV8_SWITCH_TO_EL1
operating system does not support booting at EL2, or you wish to prevent
any hypervisors from running. Supported for bootm, booti and bootefi.
+config ARMV8_DISABLE_HVC
+ bool "Disable HVC calls before switching to EL1"
+ depends on ARMV8_SWITCH_TO_EL1
+ default y
+ help
+ If switching to EL1 before loading the operating system, disable taking
+ hypercalls back to EL2. May be disabled if, for example, PSCI services are
+ running at EL2.
+
endif
diff --git a/arch/arm/include/asm/macro.h b/arch/arm/include/asm/macro.h
index 1a1edc9870..7167739210 100644
--- a/arch/arm/include/asm/macro.h
+++ b/arch/arm/include/asm/macro.h
@@ -296,9 +296,12 @@ lr .req x30
ldr \tmp2, =(ID_AA64ISAR1_EL1_GPI | ID_AA64ISAR1_EL1_GPA | \
ID_AA64ISAR1_EL1_API | ID_AA64ISAR1_EL1_APA)
tst \tmp, \tmp2
- mov \tmp2, #(HCR_EL2_RW_AARCH64 | HCR_EL2_HCD_DIS)
+ mov \tmp2, #(HCR_EL2_RW_AARCH64)
orr \tmp, \tmp2, #(HCR_EL2_APK | HCR_EL2_API)
csel \tmp, \tmp2, \tmp, eq
+#ifdef CONFIG_ARMV8_DISABLE_HVC
+ orr \tmp, \tmp, #(HCR_EL2_HCD_DIS)
+#endif
msr hcr_el2, \tmp
/* Return to the EL1_SP1 mode from EL2 */
@@ -311,7 +314,10 @@ lr .req x30
1:
/* Initialize HCR_EL2 */
- ldr \tmp, =(HCR_EL2_RW_AARCH32 | HCR_EL2_HCD_DIS)
+ ldr \tmp, =(HCR_EL2_RW_AARCH32)
+#ifdef CONFIG_ARMV8_DISABLE_HVC
+ orr \tmp, \tmp, #(HCR_EL2_HCD_DIS)
+#endif
msr hcr_el2, \tmp
/* Return to AArch32 Supervisor mode from EL2 */
diff --git a/configs/vexpress_aemv8r_defconfig b/configs/vexpress_aemv8r_defconfig
index 35e5e8a5e1..605a724a61 100644
--- a/configs/vexpress_aemv8r_defconfig
+++ b/configs/vexpress_aemv8r_defconfig
@@ -15,3 +15,4 @@ CONFIG_SYS_PROMPT="VExpress64# "
CONFIG_VIRTIO_MMIO=y
CONFIG_ARMV8_EXCEPTION_VECTORS=n
CONFIG_ARMV8_SWITCH_TO_EL1=y
+CONFIG_ARMV8_DISABLE_HVC=n
--
2.25.1
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