Re: [PATCH v17 14/20] KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Redundant NULL check on the 'kvm' pointer in kvm_vm_ioctl_enable_cap().
--

commit 849adae1adab6cdadc3f93c498689cfc52591e9d
Author: Suzuki K Poulose <suzuki.poulose@arm.com>

KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests

This commit restricts the extensions visible to realm guests to an
allowlist, as RMM v2.0 provides no mechanism for the host to perform
debug operations on the guest.

> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 3dfe0e03fab7a..fbb4d6651ab51 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
[ ... ]
> @@ -148,6 +167,9 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>  	if (is_protected_kvm_enabled() && !kvm_pkvm_ext_allowed(kvm, cap->cap))
>  		return -EINVAL;
>  
> +	if (kvm && kvm_vm_is_realm(kvm) && !kvm_realm_ext_allowed(cap->cap))

[Severity: Low]
Is the kvm && check strictly necessary in kvm_vm_ioctl_enable_cap()? 

Since this function is only called as a VM-level ioctl (dispatched from
kvm_vm_ioctl() where the pointer is extracted from the file descriptor's
private data), kvm is structurally guaranteed to be non-NULL in this
context.

While kvm_vm_ioctl_check_extension() handles global /dev/kvm calls with a
NULL kvm pointer, this function does not appear to need the same check.

> +		return -EINVAL;
> +
>  	switch (cap->cap) {
>  	case KVM_CAP_ARM_NISV_TO_USER:
>  		r = 0;
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260908162223.1683432-1-suzuki.poulose@arm.com?part=14