Re: [PATCH v19 11/20] KVM: arm64: Mandate VGIC v3 for for VMs running on hyp that don't trust the host

[Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>]

On Sun, 20 Sep 2026 22:28:36 +0100
Suzuki K Poulose <suzuki.poulose@arm.com> wrote:

> pKVM and RMM, both do not trust the host. Add a helper to detect the VMs

Maybe don't mention RMM yet, or make it clear that isn't here in this
patch.

> that have "distrusting" hyp. Use this for blocking ioremap of vgic-v2 into
> stage2 and prevent creation of VGIC other than v3.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

Other than minor comments, it feels to me like these first 11
patches are good cleanup even without the RMM stuff that follows.
Perhaps can get these upstream faster than the rest?

Jonathan

> ---
> Changes since v18:
>  - Cover pKVM guests for VGIC v3 mandate.
>  - Merge the VGIC mandate check in here.
> ---
>  arch/arm64/include/asm/kvm_host.h | 3 +++
>  arch/arm64/kvm/mmu.c              | 2 +-
>  arch/arm64/kvm/vgic/vgic-init.c   | 2 ++
>  3 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3211543a85b38..bb156a633ab75 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -328,6 +328,8 @@ enum fgt_group_id {
>  enum kvm_arm_vm_flavor {
>  	VM_NVHE,
>  	VM_VHE,
> +	/* VMs running on a hyp that doesn't trust */
> +	MARKER(__VM_DISTRUSTING_HYP),
>  	VM_PKVM,		/* Normal guests on pKVM */
>  	MARKER(__VM_PROTECTED),
>  	VM_PROTECTED_PKVM,	/* Protected VM */
> @@ -1546,6 +1548,7 @@ struct kvm *kvm_arch_alloc_vm(void);
>  #define kvm_vm_is_unprotected_pkvm(kvm)		\
>  	(is_protected_kvm_enabled() && ((kvm)->arch.vm_flavor == VM_PKVM))
>  
> +#define kvm_vm_hyp_is_distrusting(kvm)	((kvm)->arch.vm_flavor >= __VM_DISTRUSTING_HYP)
>  
>  int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature);
>  bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index cf293d09e940a..413c4b114d75d 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1251,7 +1251,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>  				     KVM_PGTABLE_PROT_R |
>  				     (writable ? KVM_PGTABLE_PROT_W : 0);
>  
> -	if (is_protected_kvm_enabled())
> +	if (kvm_vm_hyp_is_distrusting(kvm))
>  		return -EPERM;
>  
>  	size += offset_in_page(guest_ipa);
> diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
> index 4012df6002ea6..874025513afcc 100644
> --- a/arch/arm64/kvm/vgic/vgic-init.c
> +++ b/arch/arm64/kvm/vgic/vgic-init.c
> @@ -84,6 +84,8 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>  		!kvm_vgic_global_state.can_emulate_gicv2)
>  		return -ENODEV;
>  
> +	if (kvm_vm_hyp_is_distrusting(kvm) && type != KVM_DEV_TYPE_ARM_VGIC_V3)
> +		return -ENODEV;
>  	/*
>  	 * Ensure mutual exclusion with vCPU creation and any vCPU ioctls by:
>  	 *