[PATCH v5] KVM: arm64: Ignore kvm-arm.mode if !is_hyp_mode_available()

[Elliot Berman]

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 at quicinc.com>
---
 arch/arm64/kvm/arm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 8fe73ee5fa84..34cd0570e433 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2271,6 +2271,16 @@ 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;
@@ -2285,11 +2295,6 @@ 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);

base-commit: 0982c8d859f8f7022b9fd44d421c7ec721bb41f9
-- 
2.25.1