[PATCH v7 17/23] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0

From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	David Brazdil <dbrazdil@google.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Jing Zhang <jingzhangos@google.com>,
	Ajay Patil <pajay@qti.qualcomm.com>,
	Prasad Sodagudi <psodagud@codeaurora.org>,
	Srinivas Ramana <sramana@codeaurora.org>,
	Hector Martin <marcan@marcan.st>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	kernel-team@android.com
Subject: [PATCH v7 17/23] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0
Date: Mon,  8 Feb 2021 09:57:26 +0000	[thread overview]
Message-ID: <20210208095732.3267263-18-maz@kernel.org> (raw)
In-Reply-To: <20210208095732.3267263-1-maz@kernel.org>

Admitedly, passing id_aa64mmfr1.vh=0 on the command-line isn't
that easy to understand, and it is likely that users would much
prefer write "kvm-arm.mode=nvhe", or "...=protected".

So here you go. This has the added advantage that we can now
always honor the "kvm-arm.mode=protected" option, even when
booting on a VHE system.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Brazdil <dbrazdil@google.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/arm64/kernel/idreg-override.c              | 2 ++
 arch/arm64/kvm/arm.c                            | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9e3cdb271d06..2786fd39a047 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 226bac544e20..b994d689d6fb 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -45,6 +45,8 @@ static const struct {
 	char	alias[FTR_ALIAS_NAME_LEN];
 	char	feature[FTR_ALIAS_OPTION_LEN];
 } aliases[] __initconst = {
+	{ "kvm-arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
+	{ "kvm-arm.mode=protected",	"id_aa64mmfr1.vh=0" },
 };
 
 static int __init find_field(const char *cmdline,
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 04c44853b103..597565a65ca2 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1966,6 +1966,9 @@ static int __init early_kvm_mode_cfg(char *arg)
 		return 0;
 	}
 
+	if (strcmp(arg, "nvhe") == 0 && !WARN_ON(is_kernel_in_hyp_mode()))
+		return 0;
+
 	return -EINVAL;
 }
 early_param("kvm-arm.mode", early_kvm_mode_cfg);
-- 
2.29.2

