Re: [PATCHv2 5/7] KVM: PPC: Book3S HV nestedv2: reject vCPU ids beyond the PAPR limit

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] KVM: PPC: undeclared KVM_MAX_VCPU_IDS_NESTEDv2 in kvm_arch_vcpu_precreate()
--

commit f56e9e3141b7693c524f0cc29414b94ab8a0b784
Author: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

KVM: PPC: Book3S HV nestedv2: reject vCPU ids beyond the PAPR limit

This commit adds a check in kvm_arch_vcpu_precreate() on Book3S HV nestedv2
to reject vCPU IDs at or above KVM_MAX_VCPU_IDS_NESTEDv2 with -EINVAL before
reaching the H_GUEST_CREATE_VCPU hcall.

> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 9194cf492d1ca..f82d3545b39ad 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -772,6 +772,9 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>  
>  int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
>  {
> +	if (kvmhv_is_nestedv2() && id >= KVM_MAX_VCPU_IDS_NESTEDv2)
> +		return -EINVAL;

[Severity: Medium]
Is this missing the prerequisite patch referenced in the commit message?

In arch/powerpc/kvm/powerpc.c, kvm_arch_vcpu_precreate() compares id against
KVM_MAX_VCPU_IDS_NESTEDv2, which is not defined anywhere in the tree, causing
compilation of arch/powerpc/kvm/powerpc.c to fail with an undeclared
identifier error.

In addition, kvm_vm_ioctl_check_extension() in arch/powerpc/kvm/powerpc.c
still returns KVM_MAX_VCPU_IDS unconditionally for KVM_CAP_MAX_VCPU_ID:

	case KVM_CAP_MAX_VCPU_ID:
		r = KVM_MAX_VCPU_IDS;
		break;

rather than capping the capability at 2048 on nestedv2 as described in the
changelog.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/183d9a0e755f3735ebd531accb9c193cb40317ce.1793543627.git.ritesh.list@gmail.com?part=1