[PATCH v3 16/21] arm64: Make kvm-arm.mode={nvhe,protected} an alias of id_aa64mmfr1.vh=0

Marc Zyngier
2021-01-11T13:40:00Z

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>
---
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 16bc8b3b93ae..1db54878b2c4 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -41,6 +41,8 @@ static const struct {
const char * const alias;
const char * const feature;
} aliases[] __initdata = {
+ { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
+ { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
};

static int __init find_field(const char *cmdline, const struct reg_desc *reg,
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