[PATCH v2 8/8] arm64: kvm: Check support for AArch32 for 32bit guests

[Suzuki K Poulose]

Add a check to make sure the system supports AArch32 state
before initialising a 32bit guest.

Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>

---

I really wanted to pass kvm_vcpu down to the helpers. But then, I can't
define the arch specific helper in asm/kvm_host.h due to lack of kvm_vcpu's
definition yet:

 In file included from include/linux/kvm_host.h:35:0,
                  from arch/arm64/kernel/asm-offsets.c:24:
 ./arch/arm64/include/asm/kvm_host.h: In function âkvm_arch_vcpu_validate_featuresâ:
 ./arch/arm64/include/asm/kvm_host.h:344:48: error: dereferencing pointer to incomplete type
   return  !test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features) ||
---
 arch/arm/include/asm/kvm_host.h   |    5 +++++
 arch/arm/kvm/arm.c                |    3 +++
 arch/arm64/include/asm/kvm_host.h |    8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index f9f2779..945c23a 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -238,6 +238,11 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 
+static inline bool kvm_arch_vcpu_validate_features(struct kvm_vcpu_arch *arch_vcpu)
+{
+	return true;
+}
+
 static inline void kvm_arm_init_debug(void) {}
 static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index dda1959..fc4ea37 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -787,6 +787,9 @@ static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
 			set_bit(i, vcpu->arch.features);
 	}
 
+	if (!kvm_arch_vcpu_validate_features(&vcpu->arch))
+		return -EINVAL;
+
 	vcpu->arch.target = phys_target;
 
 	/* Now we know what it is, we can reset it. */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 689d4c9..9d60a6c 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -24,6 +24,8 @@
 
 #include <linux/types.h>
 #include <linux/kvm_types.h>
+#include <asm/cpufeature.h>
+#include <asm/kvm_arm.h>
 #include <asm/kvm.h>
 #include <asm/kvm_mmio.h>
 
@@ -338,6 +340,12 @@ static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
 
+static inline bool kvm_arch_vcpu_validate_features(struct kvm_vcpu_arch *arch_vcpu)
+{
+	return  !test_bit(KVM_ARM_VCPU_EL1_32BIT, arch_vcpu->features) ||
+		system_supports_32bit_el0();
+}
+
 void kvm_arm_init_debug(void);
 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
-- 
1.7.9.5