Re: [PATCH 1/5] arm/arm64: KVM: Don't BUG_ON if IT bits are set in ARM mode

Christoffer Dall
2016-09-01T11:53:56Z

On Fri, Aug 19, 2016 at 01:38:11PM +0100, Marc Zyngier wrote:
> The ARM ARM asserts that having the IT bits set in ARM mode is
> unpredictable. But should a CPU do that (and still be able to
> run correctly), we shouldn't kill the system.
>
> So let's drop the BUG_ON that checks for this, as it is not
> very helpful.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

not sure how this relates to the series, but looks fine otherwise:

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

> ---
> arch/arm/kvm/emulate.c | 4 +---
> arch/arm64/kvm/emulate.c | 4 +---
> 2 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/kvm/emulate.c b/arch/arm/kvm/emulate.c
> index af93e3f..eda9ddd 100644
> --- a/arch/arm/kvm/emulate.c
> +++ b/arch/arm/kvm/emulate.c
> @@ -221,9 +221,7 @@ static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
> unsigned long cpsr = *vcpu_cpsr(vcpu);
> bool is_arm = !(cpsr & PSR_T_BIT);
>
> - BUG_ON(is_arm && (cpsr & PSR_IT_MASK));
> -
> - if (!(cpsr & PSR_IT_MASK))
> + if (is_arm || !(cpsr & PSR_IT_MASK))
> return;
>
> cond = (cpsr & 0xe000) >> 13;
> diff --git a/arch/arm64/kvm/emulate.c b/arch/arm64/kvm/emulate.c
> index f87d8fb..df76590 100644
> --- a/arch/arm64/kvm/emulate.c
> +++ b/arch/arm64/kvm/emulate.c
> @@ -120,9 +120,7 @@ static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
> unsigned long cpsr = *vcpu_cpsr(vcpu);
> bool is_arm = !(cpsr & COMPAT_PSR_T_BIT);
>
> - BUG_ON(is_arm && (cpsr & COMPAT_PSR_IT_MASK));
> -
> - if (!(cpsr & COMPAT_PSR_IT_MASK))
> + if (is_arm || !(cpsr & COMPAT_PSR_IT_MASK))
> return;
>
> cond = (cpsr & 0xe000) >> 13;
> --
> 2.1.4
>