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Sun, 01 Nov 2026 06:47:11 -0800 (PST) Received: from pve-server.rlab ([49.205.216.49]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36a42a6f7f9sm32747545eec.25.2026.11.01.06.47.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Nov 2026 06:47:10 -0800 (PST) From: "Ritesh Harjani (IBM)" To: linuxppc-dev@lists.ozlabs.org Cc: Madhavan Srinivasan , Venkat Rao Bagalkote , linux-kernel@vger.kernel.org, chleroy@kernel.org, Michael Ellerman , Nicholas Piggin , kvm@vger.kernel.org, Anushree Mathur , Harsh Prateek Bora , "Ritesh Harjani (IBM)" Subject: [PATCHv2 5/7] KVM: PPC: Book3S HV nestedv2: reject vCPU ids beyond the PAPR limit Date: Sun, 1 Nov 2026 20:16:30 +0530 Message-Id: <183d9a0e755f3735ebd531accb9c193cb40317ce.1793543627.git.ritesh.list@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The previous patch caps KVM_CAP_MAX_VCPU_ID at 2048 on nestedv2 but nothing actually enforces it. The generic KVM_CREATE_VCPU path only checks the id against KVM_MAX_VCPU_IDS, which is 8 * NR_CPUS on HV. That means a VMM that ignores the capability can still pass a larger id. That id goes all the way down to H_GUEST_CREATE_VCPU, where the L0 rejects it and prints, ... KVM: Create Guest vcpu hcall failed, rc=-56 ...for every such attempt before failing the ioctl with -EINVAL anyway. Check the id in kvm_arch_vcpu_precreate() instead so it fails early with the same -EINVAL. Note that PowerNV and nestedv1 are not affected. Signed-off-by: Ritesh Harjani (IBM) --- arch/powerpc/kvm/powerpc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index cf620b6534de..5f9cfc34bec2 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -778,6 +778,9 @@ 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; + return 0; } -- 2.39.5