Re: [PATCH 4/4] arm64: mte: Use stage-2 NoTagAccess memory attribute if supported

[Oliver Upton]

On Mon, Oct 28, 2024 at 03:10:14PM +0530, Aneesh Kumar K.V (Arm) wrote:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 637efc055145..a8268a164c4d 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -178,6 +178,7 @@ struct kvm_xen_exit {
>  #define KVM_EXIT_NOTIFY           37
>  #define KVM_EXIT_LOONGARCH_IOCSR  38
>  #define KVM_EXIT_MEMORY_FAULT     39
> +#define KVM_EXIT_ARM_NOTAG_ACCESS 40
>  
>  /* For KVM_EXIT_INTERNAL_ERROR */
>  /* Emulate instruction failed. */
> @@ -446,6 +447,12 @@ struct kvm_run {
>  			__u64 gpa;
>  			__u64 size;
>  		} memory_fault;
> +		/* KVM_EXIT_ARM_NOTAG_ACCESS */
> +		struct {
> +			__u64 flags;
> +			__u64 gpa;
> +			__u64 size;
> +		} notag_access;

Can you please look into reusing the memory fault exit infrastructure?

The entire point of that is for KVM to tell the VMM it cannot make
forward progress because of ${SOMETHING} unexpected at the specified
GPA. You can add a new flag that describes tag access.

-- 
Thanks,
Oliver