[PATCH 3/5] ARM: KVM: make sure maintainance operation complete before world switch

[Christoffer Dall]

On Wed, Jun 19, 2013 at 02:20:04PM +0100, Marc Zyngier wrote:
> We may have preempted the guest while it was performing a maintainance
> operation (TLB invalidation, for example). Make sure it completes
> before we do anything else by adding the necessary barriers.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>  arch/arm/kvm/interrupts.S | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index afa6c04..3124e0f 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -149,6 +149,15 @@ __kvm_vcpu_return:
>  	 * r0: vcpu pointer
>  	 * r1: exception code
>  	 */
> +
> +	/*
> +	 * We may have preempted the guest while it was performing a
> +	 * maintainance operation (TLB invalidation, for example). Make
> +	 * sure it completes before we do anything else.
> +	 */

Can you explain what could go wrong here without these two instructions?

> +	dsb
> +	isb
> +
>  	save_guest_regs
>  
>  	@ Set VMID == 0
> -- 
> 1.8.2.3
> 
> 
> 
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