Subject: [PATCH 14/17] arm64: Add an aliasing facility for the idreg override

From: Marc Zyngier <[email-masked]>
Date: Mon, 28 Dec 2020 10:49:55 +0000

In order to map the override of idregs to options that a user
can easily understand, let's introduce yet another option
array, which maps an option to the corresponding idreg options.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 .../admin-guide/kernel-parameters.txt         |  3 +++
 arch/arm64/kernel/idreg-override.c            | 20 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c722ec19cd00..e88e17bf5557 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2257,6 +2257,9 @@
 	kvm-arm.mode=
 			[KVM,ARM] Select one of KVM/arm64's modes of operation.
 
+			nvhe: Standard nVHE-based mode, without support for
+			      protected guests.
+
 			protected: nVHE-based mode with support for guests whose
 				   state is kept private from the host.
 				   Not valid if the kernel is running in EL2.
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 76f3d481535d..8f64100e0b1b 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -37,6 +37,12 @@ static const struct reg_desc * const regs[] __initdata = {
 	&mmfr1,
 };
 
+static const struct {
+	const char * const	alias;
+	const char * const	feature;
+} aliases[] __initdata = {
+};
+
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
 			     int f, u64 *v)
 {
@@ -77,6 +83,18 @@ static void __init match_options(const char *cmdline)
 	}
 }
 
+static __init void match_aliases(const char *cmdline)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(aliases); i++) {
+		char *str = strstr(cmdline, aliases[i].alias);
+
+		if ((str == cmdline || (str > cmdline && *(str - 1) == ' ')))
+			match_options(aliases[i].feature);
+	}
+}
+
 static __init void parse_cmdline(void)
 {
 	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
@@ -97,6 +115,7 @@ static __init void parse_cmdline(void)
 			goto out;
 
 		match_options(prop);
+		match_aliases(prop);
 
 		if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
 			return;
@@ -104,6 +123,7 @@ static __init void parse_cmdline(void)
 
 out:
 	match_options(CONFIG_CMDLINE);
+	match_aliases(CONFIG_CMDLINE);
 }
 
 void __init init_shadow_regs(void)
-- 
2.29.2

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