[PATCH v2 3/4] KVM: arm64: Enforce reserved bits for PSCI target affinities

[Oliver Upton <oupton@google.com>]

According to the PSCI specification, ARM DEN 0022D, 5.1.4 "CPU_ON", the
CPU_ON function takes a target_cpu argument that is bit-compatible with
the affinity fields in MPIDR_EL1. All other bits in the argument are
RES0. Note that the same constraints apply to the target_affinity
argument for the AFFINITY_INFO call.

Enforce the spec by returning INVALID_PARAMS if a guest incorrectly sets
a RES0 bit.

Signed-off-by: Oliver Upton <oupton@google.com>
---
 arch/arm64/kvm/psci.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index db4056ecccfd..74c47d420253 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -59,6 +59,12 @@ static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
 	kvm_vcpu_kick(vcpu);
 }
 
+static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu,
+					   unsigned long affinity)
+{
+	return !(affinity & ~MPIDR_HWID_BITMASK);
+}
+
 static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
 {
 	struct vcpu_reset_state *reset_state;
@@ -66,9 +72,9 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
 	struct kvm_vcpu *vcpu = NULL;
 	unsigned long cpu_id;
 
-	cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK;
-	if (vcpu_mode_is_32bit(source_vcpu))
-		cpu_id &= ~((u32) 0);
+	cpu_id = smccc_get_arg1(source_vcpu);
+	if (!kvm_psci_valid_affinity(source_vcpu, cpu_id))
+		return PSCI_RET_INVALID_PARAMS;
 
 	vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
 
@@ -126,6 +132,9 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 	target_affinity = smccc_get_arg1(vcpu);
 	lowest_affinity_level = smccc_get_arg2(vcpu);
 
+	if (!kvm_psci_valid_affinity(vcpu, target_affinity))
+		return PSCI_RET_INVALID_PARAMS;
+
 	/* Determine target affinity mask */
 	target_affinity_mask = psci_affinity_mask(lowest_affinity_level);
 	if (!target_affinity_mask)
-- 
2.33.0.rc1.237.g0d66db33f3-goog

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