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AJvYcCWLcglJi3vaOcxXcj81aDRSGMggTCfaOUxBXJuMufc9/eds9L9BRYctVV8G0GFK9xQ6vN7mF9eDRQ==@kvack.org X-Gm-Message-State: AOJu0YyyESAFDldkTqzOJlPQBQPwCqaJyF9SGIy1JZKNknvoOW3ZqeMs z2876s1hLHAHtSeYiDE2lQK4tsu7bNeNwOIa6VHJFBwNiQfPzQWgFoX7aXUSPGQ6zThuG0UsRhW HXG1CgLvfeMDJfhnj+u0G5kcdjQ== X-Google-Smtp-Source: AGHT+IGwxAeNTPtzLvu/Zk8STiamMAryG8fKxvXZatC28J4mfBlAiSQlIt+hBpVpayKRInn/obOZc8kpR+KnyIdqIw== X-Received: from pjbiq12.prod.google.com ([2002:a17:90a:fb4c:b0:32b:ae4c:196c]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:2d8b:b0:32e:23fe:fa51 with SMTP id 98e67ed59e1d1-33bcf867404mr28930141a91.9.1761151911659; Wed, 22 Oct 2025 09:51:51 -0700 (PDT) Date: Wed, 22 Oct 2025 09:51:49 -0700 In-Reply-To: <2457cb3b-5dde-4ca1-b75d-174b5daee28a@arm.com> Mime-Version: 1.0 References: <8ee16fbf254115b0fd72cc2b5c06d2ccef66eca9.1760731772.git.ackerleytng@google.com> <2457cb3b-5dde-4ca1-b75d-174b5daee28a@arm.com> Message-ID: Subject: Re: [RFC PATCH v1 07/37] KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2 From: Ackerley Tng To: Steven Price , cgroups@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Cc: akpm@linux-foundation.org, binbin.wu@linux.intel.com, bp@alien8.de, brauner@kernel.org, chao.p.peng@intel.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@intel.com, dave.hansen@linux.intel.com, david@redhat.com, dmatlack@google.com, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, haibo1.xu@intel.com, hannes@cmpxchg.org, hch@infradead.org, hpa@zytor.com, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgg@ziepe.ca, jgowans@amazon.com, jhubbard@nvidia.com, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maobibo@loongson.cn, mathieu.desnoyers@efficios.com, maz@kernel.org, mhiramat@kernel.org, mhocko@kernel.org, mic@digikod.net, michael.roth@amd.com, mingo@redhat.com, mlevitsk@redhat.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, peterx@redhat.com, pgonda@google.com, prsampat@amd.com, pvorel@suse.cz, qperret@google.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, rostedt@goodmis.org, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shakeel.butt@linux.dev, shuah@kernel.org, steven.sistare@oracle.com, suzuki.poulose@arm.com, tabba@google.com, tglx@linutronix.de, thomas.lendacky@amd.com, vannapurve@google.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, wyihan@google.com, xiaoyao.li@intel.com, yan.y.zhao@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Stat-Signature: w49fdmsx7y8b9xmhcmrad69d983jfbkd X-Rspamd-Queue-Id: 1B94AC0006 X-Rspamd-Server: rspam09 X-HE-Tag: 1761151912-433273 X-HE-Meta: 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 0g7HHkav 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Steven Price writes: > On 17/10/2025 21:11, Ackerley Tng wrote: >> >> [...snip...] >> >> @@ -5366,15 +5375,35 @@ static long kvm_vm_ioctl(struct file *filp, >> } >> #endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */ >> #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES >> + case KVM_SET_MEMORY_ATTRIBUTES2: >> case KVM_SET_MEMORY_ATTRIBUTES: { >> - struct kvm_memory_attributes attrs; >> + struct kvm_memory_attributes2 attrs; >> + unsigned long size; >> + >> + if (ioctl == KVM_SET_MEMORY_ATTRIBUTES) { >> + /* >> + * Fields beyond struct kvm_userspace_memory_region shouldn't be >> + * accessed, but avoid leaking kernel memory in case of a bug. >> + */ >> + memset(&mem, 0, sizeof(mem)); > > s/mem/attrs/g > >> + size = sizeof(struct kvm_set_memory_attributes); >> + } else { >> + size = sizeof(struct kvm_set_memory_attributes2); > > s/kvm_set_memory_attributes/kvm_memory_attributes/ (on both sizeof lines > above and in the SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD macro). > >> + } >> + >> + /* Ensure the common parts of the two structs are identical. */ >> + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(slot); >> + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(flags); >> + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(guest_phys_addr); >> + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(memory_size); >> + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(userspace_addr); > > The fields are: > * address > * size > * attributes > * flags > > The list you've got appears to match struct kvm_userspace_memory_region > - copy/paste error? > Yes I did copy/paste this from KVM_SET_USER_MEMORY_REGION2. Thanks for catching this! I missed out build-testing this with CONFIG_KVM_VM_MEMORY_ATTRIBUTES. I've done that and here's a replacement patch. > Thanks, > Steve > >> >> [...snip...] >> >From 31283972574bde2ffa1960d30c80286f8467c594 Mon Sep 17 00:00:00 2001 From: Ackerley Tng Date: Thu, 16 Oct 2025 11:48:01 -0700 Subject: [PATCH] KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2 Introduce a "version 2" of KVM_SET_MEMORY_ATTRIBUTES to support returning information back to userspace. This new ioctl and structure will, in a later patch, be shared as a guest_memfd ioctl, where the padding in the new kvm_memory_attributes2 structure will be for writing the response from the guest_memfd ioctl to userspace. A new ioctl is necessary for these reasons: 1. KVM_SET_MEMORY_ATTRIBUTES is currently a write-only ioctl and does not allow userspace to read fields. There's nothing in code (yet?) that validates this, but using _IOWR for consistency would be prudent. 2. KVM_SET_MEMORY_ATTRIBUTES, when used as a guest_memfd ioctl, will need an additional field to provide userspace with more error details. Alternatively, a completely new ioctl could be defined, unrelated to KVM_SET_MEMORY_ATTRIBUTES, but using the same ioctl number and struct for the vm and guest_memfd ioctls streamlines the interface for userspace. In addition, any memory attributes, implemented on the vm or guest_memfd ioctl, can be easily shared with the other. Suggested-by: Sean Christopherson Change-Id: I50cd506d9a28bf68a90e659015603de579569bc1 Signed-off-by: Ackerley Tng --- Documentation/virt/kvm/api.rst | 32 ++++++++++++++++++++++++++++++++ include/uapi/linux/kvm.h | 12 ++++++++++++ virt/kvm/kvm_main.c | 34 +++++++++++++++++++++++++++++++--- 3 files changed, 75 insertions(+), 3 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 754b662a453c3..a812769d79bf6 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6355,6 +6355,8 @@ S390: Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set. Returns -EINVAL if called on a protected VM. +.. _KVM_SET_MEMORY_ATTRIBUTES: + 4.141 KVM_SET_MEMORY_ATTRIBUTES ------------------------------- @@ -6512,6 +6514,36 @@ the capability to be present. `flags` must currently be zero. +4.144 KVM_SET_MEMORY_ATTRIBUTES2 +--------------------------------- + +:Capability: KVM_CAP_MEMORY_ATTRIBUTES2 +:Architectures: x86 +:Type: vm ioctl +:Parameters: struct kvm_memory_attributes2 (in/out) +:Returns: 0 on success, <0 on error + +KVM_SET_MEMORY_ATTRIBUTES2 is an extension to +KVM_SET_MEMORY_ATTRIBUTES that supports returning (writing) values to +userspace. The original (pre-extension) fields are shared with +KVM_SET_MEMORY_ATTRIBUTES identically. + +Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES. + +:: + + struct kvm_memory_attributes2 { + __u64 address; + __u64 size; + __u64 attributes; + __u64 flags; + __u64 reserved[4]; + }; + + #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) + +See also: :ref: `KVM_SET_MEMORY_ATTRIBUTES`. + .. _kvm_run: diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 52f6000ab0208..c300e38c7c9cd 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -963,6 +963,7 @@ struct kvm_enable_cap { #define KVM_CAP_RISCV_MP_STATE_RESET 242 #define KVM_CAP_ARM_CACHEABLE_PFNMAP_SUPPORTED 243 #define KVM_CAP_GUEST_MEMFD_FLAGS 244 +#define KVM_CAP_MEMORY_ATTRIBUTES2 245 struct kvm_irq_routing_irqchip { __u32 irqchip; @@ -1617,4 +1618,15 @@ struct kvm_pre_fault_memory { __u64 padding[5]; }; +/* Available with KVM_CAP_MEMORY_ATTRIBUTES2 */ +#define KVM_SET_MEMORY_ATTRIBUTES2 _IOWR(KVMIO, 0xd6, struct kvm_memory_attributes2) + +struct kvm_memory_attributes2 { + __u64 address; + __u64 size; + __u64 attributes; + __u64 flags; + __u64 reserved[4]; +}; + #endif /* __LINUX_KVM_H */ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 35166754a22b4..95aa51b334a70 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2621,7 +2621,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end, return r; } static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, - struct kvm_memory_attributes *attrs) + struct kvm_memory_attributes2 *attrs) { gfn_t start, end; @@ -4959,6 +4959,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) case KVM_CAP_DEVICE_CTRL: return 1; #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES + case KVM_CAP_MEMORY_ATTRIBUTES2: case KVM_CAP_MEMORY_ATTRIBUTES: if (!vm_memory_attributes) return 0; @@ -5184,6 +5185,14 @@ do { \ sizeof_field(struct kvm_userspace_memory_region2, field)); \ } while (0) +#define SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(field) \ +do { \ + BUILD_BUG_ON(offsetof(struct kvm_memory_attributes, field) != \ + offsetof(struct kvm_memory_attributes2, field)); \ + BUILD_BUG_ON(sizeof_field(struct kvm_memory_attributes, field) != \ + sizeof_field(struct kvm_memory_attributes2, field)); \ +} while (0) + static long kvm_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { @@ -5366,15 +5375,34 @@ static long kvm_vm_ioctl(struct file *filp, } #endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */ #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES + case KVM_SET_MEMORY_ATTRIBUTES2: case KVM_SET_MEMORY_ATTRIBUTES: { - struct kvm_memory_attributes attrs; + struct kvm_memory_attributes2 attrs; + unsigned long size; + + if (ioctl == KVM_SET_MEMORY_ATTRIBUTES) { + /* + * Fields beyond struct kvm_userspace_memory_region shouldn't be + * accessed, but avoid leaking kernel memory in case of a bug. + */ + memset(&attrs, 0, sizeof(attrs)); + size = sizeof(struct kvm_memory_attributes); + } else { + size = sizeof(struct kvm_memory_attributes2); + } + + /* Ensure the common parts of the two structs are identical. */ + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(address); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(size); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(attributes); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(flags); r = -ENOTTY; if (!vm_memory_attributes) goto out; r = -EFAULT; - if (copy_from_user(&attrs, argp, sizeof(attrs))) + if (copy_from_user(&attrs, argp, size)) goto out; r = kvm_vm_ioctl_set_mem_attributes(kvm, &attrs); -- 2.51.0.915.g61a8936c21-goog