linux-kernel - [PATCH v4 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line

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Date:   Mon, 18 Jan 2021 09:45:25 +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 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line

As we want to be able to disable VHE at runtime, let's match
"id_aa64mmfr1.vh=" from the command line as an override.
This doesn't have much effect yet as our boot code doesn't look
at the cpufeature, but only at the HW registers.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/include/asm/cpufeature.h |  3 +++
 arch/arm64/kernel/cpufeature.c      |  6 +++++-
 arch/arm64/kernel/idreg-override.c  | 12 ++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index fe0130d6c0ff..80a5f423444e 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -814,6 +814,9 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
 	return 8;
 }
 
+extern u64 id_aa64mmfr1_val;
+extern u64 id_aa64mmfr1_mask;
+
 u32 get_kvm_ipa_limit(void);
 void dump_cpu_features(void);
 
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 48a011935d8c..5b9343d2e9f0 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -555,6 +555,9 @@ static const struct arm64_ftr_bits ftr_raz[] = {
 
 #define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL)
 
+u64 id_aa64mmfr1_val;
+u64 id_aa64mmfr1_mask;
+
 static const struct __ftr_reg_entry {
 	u32			sys_id;
 	struct arm64_ftr_reg 	*reg;
@@ -602,7 +605,8 @@ static const struct __ftr_reg_entry {
 
 	/* Op1 = 0, CRn = 0, CRm = 7 */
 	ARM64_FTR_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0),
-	ARM64_FTR_REG(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1),
+	ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64MMFR1_EL1, ftr_id_aa64mmfr1,
+			       &id_aa64mmfr1_val, &id_aa64mmfr1_mask),
 	ARM64_FTR_REG(SYS_ID_AA64MMFR2_EL1, ftr_id_aa64mmfr2),
 
 	/* Op1 = 0, CRn = 1, CRm = 2 */
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 392f93b67103..75d9845f489b 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -10,6 +10,7 @@
 #include <linux/libfdt.h>
 
 #include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
 #include <asm/setup.h>
 
 struct reg_desc {
@@ -22,7 +23,18 @@ struct reg_desc {
 	} 			fields[];
 };
 
+static const struct reg_desc mmfr1 __initdata = {
+	.name		= "id_aa64mmfr1",
+	.val		= &id_aa64mmfr1_val,
+	.mask		= &id_aa64mmfr1_mask,
+	.fields		= {
+	        { "vh", ID_AA64MMFR1_VHE_SHIFT },
+		{}
+	},
+};
+
 static const struct reg_desc * const regs[] __initdata = {
+	&mmfr1,
 };
 
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
-- 
2.29.2