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[175.34.62.5]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-318c1523351sm10913306a91.48.2025.06.30.23.38.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Jun 2025 23:38:53 -0700 (PDT) Message-ID: Date: Tue, 1 Jul 2025 16:38:44 +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 v9 09/43] KVM: arm64: Allow passing machine type in KVM creation To: Steven Price , kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , 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 References: <20250611104844.245235-1-steven.price@arm.com> <20250611104844.245235-10-steven.price@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <20250611104844.245235-10-steven.price@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/11/25 8:48 PM, Steven Price wrote: > Previously machine type was used purely for specifying the physical > address size of the guest. Reserve the higher bits to specify an ARM > specific machine type and declare a new type 'KVM_VM_TYPE_ARM_REALM' > used to create a realm guest. > > Reviewed-by: Suzuki K Poulose > Reviewed-by: Gavin Shan > Signed-off-by: Steven Price > --- > Changes since v7: > * Add some documentation explaining the new machine type. > Changes since v6: > * Make the check for kvm_rme_is_available more visible and report an > error code of -EPERM (instead of -EINVAL) to make it explicit that > the kernel supports RME, but the platform doesn't. > --- > Documentation/virt/kvm/api.rst | 16 ++++++++++++++-- > arch/arm64/kvm/arm.c | 15 +++++++++++++++ > arch/arm64/kvm/mmu.c | 3 --- > include/uapi/linux/kvm.h | 19 +++++++++++++++---- > 4 files changed, 44 insertions(+), 9 deletions(-) > One nitpick below. > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 65543289f75c..0049d67fe38f 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -181,8 +181,20 @@ flag KVM_VM_MIPS_VZ. > ARM64: > ^^^^^^ > > -On arm64, the physical address size for a VM (IPA Size limit) is limited > -to 40bits by default. The limit can be configured if the host supports the > +On arm64, the machine type identifier is used to encode a type and the > +physical address size for the VM. The lower byte (bits[7-0]) encode the > +address size and the upper bits[11-8] encode a machine type. The machine > +types that might be available are: > + > + ====================== ============================================ > + KVM_VM_TYPE_ARM_NORMAL A standard VM > + KVM_VM_TYPE_ARM_REALM A "Realm" VM using the Arm Confidential > + Compute extensions, the VM's memory is > + protected from the host. > + ====================== ============================================ > + > +The physical address size for a VM (IPA Size limit) is limited to 40bits > +by default. The limit can be configured if the host supports the > extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use > KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type > identifier, where IPA_Bits is the maximum width of any physical > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 8080443d24af..b3e3323573c6 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -172,6 +172,21 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) > mutex_unlock(&kvm->lock); > #endif > > + if (type & ~(KVM_VM_TYPE_ARM_MASK | KVM_VM_TYPE_ARM_IPA_SIZE_MASK)) > + return -EINVAL; > + > + switch (type & KVM_VM_TYPE_ARM_MASK) { > + case KVM_VM_TYPE_ARM_NORMAL: > + break; > + case KVM_VM_TYPE_ARM_REALM: > + if (!static_branch_unlikely(&kvm_rme_is_available)) > + return -EPERM; > + kvm->arch.is_realm = true; > + break; Here we need to explicitly set the realm's state to REALM_STATE_NONE even though it's equal to zero, and the struct vm should have been cleared on allocation. WRITE_ONCE(kvm->arch.realm.state, REALM_STATE_NONE); kvm->arch.is_realm = true; break; > + default: > + return -EINVAL; > + } > + > kvm_init_nested(kvm); > > ret = kvm_share_hyp(kvm, kvm + 1); [...] Thanks, Gavin