Subject: [PATCH v3 16/17] arm64: Allow arm64_sw.hvhe on command line

From: Marc Zyngier <[email-masked]>
Date: Fri, 9 Jun 2023 17:21:59 +0100

Add the arm64_sw.hvhe=1 option to force the use of the hVHE mode
in the hypervisor code only.

This enables the hVHE mode of operation when using KVM on VHE
hardware.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/kernel/idreg-override.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 8c93b6198bf5..c553d30089e5 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -138,11 +138,22 @@ static const struct ftr_set_desc smfr0 __initconst = {
 	},
 };
 
+static bool __init hvhe_filter(u64 val)
+{
+	u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1);
+
+	return (val == 1 &&
+		lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 &&
+		cpuid_feature_extract_unsigned_field(mmfr1,
+						     ID_AA64MMFR1_EL1_VH_SHIFT));
+}
+
 static const struct ftr_set_desc sw_features __initconst = {
 	.name		= "arm64_sw",
 	.override	= &arm64_sw_feature_override,
 	.fields		= {
 		FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
+		FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter),
 		{}
 	},
 };
-- 
2.34.1

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