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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3286f95a847sm30663601eec.17.2026.08.31.21.29.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 31 Aug 2026 21:29:33 -0700 (PDT) Message-ID: <8e699e2d-c04c-4ff7-98a3-c01e573ee817@redhat.com> Date: Tue, 1 Sep 2026 14:29:22 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v16 15/45] KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests To: Steven Price , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Suzuki K Poulose , Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo Pieralisi References: <20260803134403.80630-1-steven.price@arm.com> <20260803134403.80630-16-steven.price@arm.com> From: Gavin Shan In-Reply-To: <20260803134403.80630-16-steven.price@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: NsqmXFtVon3XUJr5jm8TLsdig6GlrSBIpiWVili5zaA_1788236975 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260831_212938_632438_72AC89FD X-CRM114-Status: GOOD ( 23.44 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Steve, On 8/3/26 11:43 PM, Steven Price wrote: > From: Suzuki K Poulose > > RMM v2.0 provides no mechanism for the host to perform debug operations > on the guest. So limit the extensions that are visible to an allowlist > so that only those capabilities we can support are advertised. > > Signed-off-by: Suzuki K Poulose > Signed-off-by: Steven Price > --- > Changes since v13: > * Add missing check in kvm_vm_ioctl_enable_cap(). > Changes since v10: > * Add a kvm_realm_ext_allowed() function which limits which extensions > are exposed to an allowlist. This removes the need for special casing > various extensions. > Changes since v7: > * Remove the helper functions and inline the kvm_is_realm() check with > a ternary operator. > * Rewrite the commit message to explain this patch. > --- > arch/arm64/kvm/arm.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index c4d906861736..6f39831dcf5d 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -135,6 +135,26 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu) > return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE; > } > > +static bool kvm_realm_ext_allowed(long ext) > +{ > + switch (ext) { > + case KVM_CAP_IRQCHIP: > + case KVM_CAP_ARM_PSCI: > + case KVM_CAP_ARM_PSCI_0_2: > + case KVM_CAP_NR_VCPUS: > + case KVM_CAP_MAX_VCPUS: > + case KVM_CAP_MAX_VCPU_ID: > + case KVM_CAP_MSI_DEVID: > + case KVM_CAP_ARM_VM_IPA_SIZE: > + case KVM_CAP_ARM_PTRAUTH_ADDRESS: > + case KVM_CAP_ARM_PTRAUTH_GENERIC: > + case KVM_CAP_ARM_RMI: > + case KVM_CAP_SYNC_MMU: > + return true; > + } > + return false; > +} > + Nitpick: The code can be simplified a bit if @kvm is passed to kvm_realm_ext_allowed(). In this way, kvm_realm_ext_allowed() looks similar to kvm_pkvm_ext_allowed(). static bool kvm_realm_ext_allowed(struct kvm *kvm, long ext) { if (!kvm || !kvm_is_realm(kvm)) return true; switch (ext) { case KVM_CAP_IRQCHIP: : case KVM_CAP_SYNC_MMU: return true; } return false; } > int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > struct kvm_enable_cap *cap) > { > @@ -146,6 +166,9 @@ 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_is_realm(kvm) && !kvm_realm_ext_allowed(cap->cap)) > + return -EINVAL; > + if (!kvm_realm_ext_allowed(kvm, cap->cap)) return -EINVAL; > switch (cap->cap) { > case KVM_CAP_ARM_NISV_TO_USER: > r = 0; > @@ -380,6 +403,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > if (is_protected_kvm_enabled() && !kvm_pkvm_ext_allowed(kvm, ext)) > return 0; > > + if (kvm && kvm_is_realm(kvm) && !kvm_realm_ext_allowed(ext)) > + return 0; > + if (!kvm_realm_ext_allowed(kvm, ext)) return 0; > switch (ext) { > case KVM_CAP_IRQCHIP: > r = vgic_present; Thanks, Gavin