KVM: arm64: Ignore kvm-arm.mode if !is_hyp_mode_available()

Ignore kvm-arm.mode if !is_hyp_mode_available(). Specifically, we want
to avoid switching kvm_mode to KVM_MODE_PROTECTED if hypervisor mode is
not available. This prevents "Protected KVM" cpu capability being
reported when Linux is booting in EL1 and would not have KVM enabled.
Reasonably though, we should warn if the command line is requesting a
KVM mode at all if KVM isn't actually available. Allow
"kvm-arm.mode=none" to skip the warning since this would disable KVM
anyway.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220920190658.2880184-1-quic_eberman@quicinc.com

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 2ff0ef62abadc8cbf01a23b4b1df4f46039b55f7..c7fb2ad8be9f5dae8cfd1daff7498a6fa870575e 100644 (file)
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2270,6 +2270,16 @@ static int __init early_kvm_mode_cfg(char *arg)
        if (!arg)
                return -EINVAL;
 
+       if (strcmp(arg, "none") == 0) {
+               kvm_mode = KVM_MODE_NONE;
+               return 0;
+       }
+
+       if (!is_hyp_mode_available()) {
+               pr_warn_once("KVM is not available. Ignoring kvm-arm.mode\n");
+               return 0;
+       }
+
        if (strcmp(arg, "protected") == 0) {
                if (!is_kernel_in_hyp_mode())
                        kvm_mode = KVM_MODE_PROTECTED;
@@ -2284,11 +2294,6 @@ static int __init early_kvm_mode_cfg(char *arg)
                return 0;
        }
 
-       if (strcmp(arg, "none") == 0) {
-               kvm_mode = KVM_MODE_NONE;
-               return 0;
-       }
-
        return -EINVAL;
 }
 early_param("kvm-arm.mode", early_kvm_mode_cfg);