Re: [RFC PATCH 07/28] arm64: kvm: Allow passing machine type in KVM creation

[Zhi Wang]

On Fri, 27 Jan 2023 11:29:11 +0000
Steven Price <steven.price@xxxxxxx> wrote:

> Previously machine type was used purely for specifying the physical
> address size of the guest. Reserve the higher bits to specify an ARM
> specific machine type and declare a new type 'KVM_VM_TYPE_ARM_REALM'
> used to create a realm guest.
> 
> Signed-off-by: Steven Price <steven.price@xxxxxxx>
> ---
>  arch/arm64/kvm/arm.c     | 13 +++++++++++++
>  arch/arm64/kvm/mmu.c     |  3 ---
>  arch/arm64/kvm/reset.c   |  3 ---
>  include/uapi/linux/kvm.h | 19 +++++++++++++++----
>  4 files changed, 28 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 50f54a63732a..badd775547b8 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -147,6 +147,19 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>  {
>  	int ret;
>  
> +	if (type & ~(KVM_VM_TYPE_ARM_MASK | KVM_VM_TYPE_ARM_IPA_SIZE_MASK))
> +		return -EINVAL;
> +
> +	switch (type & KVM_VM_TYPE_ARM_MASK) {
> +	case KVM_VM_TYPE_ARM_NORMAL:
> +		break;
> +	case KVM_VM_TYPE_ARM_REALM:
> +		kvm->arch.is_realm = true;

It is better to let this call fail when !kvm_rme_is_available? It is
strange to be able to create a VM with REALM type in a system doesn't
support RME.

> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
>  	ret = kvm_share_hyp(kvm, kvm + 1);
>  	if (ret)
>  		return ret;
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index d0f707767d05..22c00274884a 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -709,9 +709,6 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
>  	u64 mmfr0, mmfr1;
>  	u32 phys_shift;
>  
> -	if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
> -		return -EINVAL;
> -
>  	phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
>  	if (is_protected_kvm_enabled()) {
>  		phys_shift = kvm_ipa_limit;
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index c165df174737..9e71d69e051f 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -405,9 +405,6 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type)
>  	if (kvm_is_realm(kvm))
>  		ipa_limit = kvm_realm_ipa_limit();
>  
> -	if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
> -		return -EINVAL;
> -
>  	phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
>  	if (phys_shift) {
>  		if (phys_shift > ipa_limit ||
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index fec1909e8b73..bcfc4d58dc19 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -898,14 +898,25 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_S390_SIE_PAGE_OFFSET 1
>  
>  /*
> - * On arm64, machine type can be used to request the physical
> - * address size for the VM. Bits[7-0] are reserved for the guest
> - * PA size shift (i.e, log2(PA_Size)). For backward compatibility,
> - * value 0 implies the default IPA size, 40bits.
> + * On arm64, machine type can be used to request both the machine type and
> + * the physical address size for the VM.
> + *
> + * Bits[11-8] are reserved for the ARM specific machine type.
> + *
> + * Bits[7-0] are reserved for the guest PA size shift (i.e, log2(PA_Size)).
> + * For backward compatibility, value 0 implies the default IPA size, 40bits.
>   */
> +#define KVM_VM_TYPE_ARM_SHIFT		8
> +#define KVM_VM_TYPE_ARM_MASK		(0xfULL << KVM_VM_TYPE_ARM_SHIFT)
> +#define KVM_VM_TYPE_ARM(_type)		\
> +	(((_type) << KVM_VM_TYPE_ARM_SHIFT) & KVM_VM_TYPE_ARM_MASK)
> +#define KVM_VM_TYPE_ARM_NORMAL		KVM_VM_TYPE_ARM(0)
> +#define KVM_VM_TYPE_ARM_REALM		KVM_VM_TYPE_ARM(1)
> +
>  #define KVM_VM_TYPE_ARM_IPA_SIZE_MASK	0xffULL
>  #define KVM_VM_TYPE_ARM_IPA_SIZE(x)		\
>  	((x) & KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
> +
>  /*
>   * ioctls for /dev/kvm fds:
>   */