[PATCH v4 16/21] arm64: Make kvm-arm.mode={nvhe,protected} an alias of id_aa64mmfr1.vh=0

[Marc Zyngier]

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 <m...@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