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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a853d0261csm2783924a91.17.2026.10.05.21.58.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Oct 2026 21:58:13 -0700 (PDT) Message-ID: Date: Tue, 6 Oct 2026 14:58:04 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v22 19/23] KVM: arm64: CCA: Don't expose unsupported capabilities for realm guests To: Suzuki K Poulose , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: maz@kernel.org, will@kernel.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, steven.price@arm.com, aneesh.kumar@kernel.org, oupton@kernel.org, joey.gouly@arm.com, tabba@google.com, yuzenghui@huawei.com, linux-coco@lists.linux.dev, gankulkarni@os.amperecomputing.com, sdonthineni@nvidia.com, alpergun@google.com, fj0570is@fujitsu.com, WeiLin.Chang@arm.com, lpieralisi@kernel.org, enju.kohei@fujitsu.com, sudeep.holla@arm.com, jonathan.cameron@oss.qualcomm.com References: <20261005090754.2140522-1-suzuki.poulose@arm.com> <20261005090754.2140522-20-suzuki.poulose@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20261005090754.2140522-20-suzuki.poulose@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/5/26 7:07 PM, Suzuki K Poulose wrote: > Limit the capabilities that are allowed for Realm VMs. Similarly block > the vm_ioctls backed by the capabilities. > > Repurpose the kvm_pkvm_ioctl_allowed() to support both pKVM and Realm > ioctls. Rename the helper to kvm_vm_ioctl_allowed() and move it > into arch/arm64/kvm/arm.c. Also add a generic kvm_vm_ext_allowed() > to handle pKVM and Realm capability filtering and route them accordingly. > > Signed-off-by: Suzuki K Poulose > --- > Changes since v21: > - Drop WARN_ON_ONCE() from kvm_vm_ioctl_allowed to synchronise with > what is in -rc5 and make the conflict resolution easier. > --- > arch/arm64/include/asm/kvm_pkvm.h | 19 ------------ > arch/arm64/include/asm/kvm_rmi.h | 24 +++++++++++++++ > arch/arm64/kvm/arm.c | 49 +++++++++++++++++++++++++++++-- > 3 files changed, 70 insertions(+), 22 deletions(-) > One nitpick below. In either way: Reviewed-by: Gavin Shan > diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h > index 2addc37c500e1..b833abb1be9c7 100644 > --- a/arch/arm64/include/asm/kvm_pkvm.h > +++ b/arch/arm64/include/asm/kvm_pkvm.h > @@ -53,25 +53,6 @@ static inline bool kvm_pkvm_ext_allowed(struct kvm *kvm, long ext) > } > } > > -/* > - * Check whether the KVM VM IOCTL is allowed in pKVM. > - * > - * Certain features are allowed only for non-protected VMs in pKVM, which is why > - * this takes the VM (kvm) as a parameter. > - */ > -static inline bool kvm_pkvm_ioctl_allowed(struct kvm *kvm, unsigned int ioctl) > -{ > - long ext; > - int r; > - > - r = kvm_get_cap_for_kvm_ioctl(ioctl, &ext); > - > - if (WARN_ON_ONCE(r < 0)) > - return false; > - > - return kvm_pkvm_ext_allowed(kvm, ext); > -} > - > extern struct memblock_region kvm_nvhe_sym(hyp_memory)[]; > extern unsigned int kvm_nvhe_sym(hyp_memblock_nr); > > diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h > index 44f5c75a27b5b..ea1450e0c8619 100644 > --- a/arch/arm64/include/asm/kvm_rmi.h > +++ b/arch/arm64/include/asm/kvm_rmi.h > @@ -6,6 +6,8 @@ > #ifndef __ASM_KVM_RMI_H > #define __ASM_KVM_RMI_H > > +#include > + > /** > * enum realm_state - State of a Realm > * > @@ -58,4 +60,26 @@ struct realm { > > void kvm_init_rmi(void); > > +static inline 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_DEVICE_CTRL: > + 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_SVE: > + case KVM_CAP_ONE_REG: > + case KVM_CAP_ARM_PTRAUTH_ADDRESS: > + case KVM_CAP_ARM_PTRAUTH_GENERIC: > + case KVM_CAP_SYNC_MMU: > + return true; > + } > + return false; > +} > + > #endif /* __ASM_KVM_RMI_H */ > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 37ef2ba4e43e2..fe707a0c47308 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -136,6 +136,49 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu) > return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE; > } > > +static inline bool kvm_vm_ext_allowed(struct kvm *kvm, long ext) > +{ > + /* > + * We could be called with kvm as NULL, so can't use kvm_vm_* for pKVM > + * flavors > + */ > + if (is_protected_kvm_enabled()) > + return kvm_pkvm_ext_allowed(kvm, ext); > + else if (kvm && kvm_vm_is_realm(kvm)) > + return kvm_realm_ext_allowed(ext); > + else > + return true; > +} > + > +/* > + * Check whether the KVM VM IOCTL is allowed. For pKVM and Realm VMs, certain > + * ioctls are not allowed. Further, certain features are allowed only for > + * non-protected VMs in pKVM. > + */ > +static inline bool kvm_vm_ioctl_allowed(struct kvm *kvm, unsigned int ioctl) > +{ > + long ext; > + int r; long ext, r; kvm_get_cap_for_kvm_ioctl() returns 'long' instead of 'int' value. > + > + /* > + * We are guaranteed to be called with a valid kvm instance, as the > + * only caller is kvm_arch_vm_ioctl(). Catch any deviations, as we > + * rely on the kvm instance below. > + */ > + if (WARN_ON_ONCE(!kvm)) > + return false; > + > + /* Cover both pKVM host and Realm VMs */ > + if (!kvm_vm_hyp_is_distrusting(kvm)) > + return true; > + > + r = kvm_get_cap_for_kvm_ioctl(ioctl, &ext); > + if (r < 0) > + return false; > + > + return kvm_vm_ext_allowed(kvm, ext); > +} > + > int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > struct kvm_enable_cap *cap) > { > @@ -144,7 +187,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > if (cap->flags) > return -EINVAL; > > - if (is_protected_kvm_enabled() && !kvm_pkvm_ext_allowed(kvm, cap->cap)) > + if (!kvm_vm_ext_allowed(kvm, cap->cap)) > return -EINVAL; > > switch (cap->cap) { > @@ -403,7 +446,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > { > int r; > > - if (is_protected_kvm_enabled() && !kvm_pkvm_ext_allowed(kvm, ext)) > + if (!kvm_vm_ext_allowed(kvm, ext)) > return 0; > > switch (ext) { > @@ -2146,7 +2189,7 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) > void __user *argp = (void __user *)arg; > struct kvm_device_attr attr; > > - if (is_protected_kvm_enabled() && !kvm_pkvm_ioctl_allowed(kvm, ioctl)) > + if (!kvm_vm_ioctl_allowed(kvm, ioctl)) > return -EINVAL; > > switch (ioctl) { Thanks, Gavin