On 02/03/16 09:08, Marc Zyngier wrote:
On 25/02/16 09:52, Suzuki K Poulose wrote:
Add a check to make sure the system supports AArch32 state
before initialising a 32bit guest.

Cc: Christoffer Dall <christoffer.d...@linaro.org>
Cc: Marc Zyngier <marc.zyng...@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>

...

@@ -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();
+}
+

This is really convoluted (it took me 5 minutes staring at the
expression and remembering that AArch32 EL1 implies AArch32 EL0 to get it).

Now, we already have kvm_reset_vcpu() that validates AArch32 support. It
would probably be better to move things there. Thoughts?

I think we can leave the kvm bits as it is now, discarding this patch, as
we already do the right thing. Also system_supports_32bit_el0() doesn't
guarantee system_supports_32bit_el1(). The negation and converse are
both true though.

i.e,

        !32bit_el0_support => !32bit_el1_support
                  &
        32bit_el1_support => 32bit_el0_support

Thanks
Suzuki

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