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AJvYcCVqroxgsH9LaRN4YrxCY0KEDR2vTCkWr5qgPUqflwcg14ZDx1dtnEIgI/JNlgtksrB2OwgClRXATw==@kvack.org X-Gm-Message-State: AOJu0YxQ2vZSWq2OkCQvSYlsB413aqPI9vp1hReWAdfvKY8lZ7YOcz4t iHuf2a5pA59symwTblp/fA9VMaJRTG+u7JqWwCGNA540GvmNMrAmCCukcfwtee64Sb789NyrN3f oJPJ+Bg== X-Google-Smtp-Source: AGHT+IFg265zLGl2bQmWCvkKPU4u2q3qfh913c9juw3tQPbolW7ChzJ4nSIfXk8wuAQ4jQwhmqRekZFnQlI= X-Received: from pjnj13.prod.google.com ([2002:a17:90a:840d:b0:329:7261:93b6]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:3d84:b0:2f9:39b0:fd88 with SMTP id adf61e73a8af0-334a84da4b1mr29081038637.21.1761175851395; Wed, 22 Oct 2025 16:30:51 -0700 (PDT) Date: Wed, 22 Oct 2025 16:30:49 -0700 In-Reply-To: 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: Sean Christopherson To: Ackerley Tng Cc: 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, 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, 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, shakeel.butt@linux.dev, shuah@kernel.org, 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, 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 Content-Type: text/plain; charset="us-ascii" X-Stat-Signature: pkeqmhxbg7h5rga5xwfs4rfwujou4f4k X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B57E48000C X-HE-Tag: 1761175852-971090 X-HE-Meta: U2FsdGVkX1+GIo/l1S3YYNhd136ZOEWKOAMZ2XB8h/MtSDwkwXAEgYoB/VUpueJG5WLlsx2xj9dTEFNvWVKteLgjh5rYMqBoAQ+Ae0AWOM6CpgCutu9uHUku8QLlrxAn+GID2h+lmii8EO1HitNE+aGH+3aU7T6zD/I2IT7FIlLEp2M+73SG2O8939AccXxFBgFYWZ+6lHzUwWnkUk6MDySnEKEiy3GoOibaHXosFk+lmyoxvBdRbYU31yytCREY66wl0IQ6Sfxg4WFuE3qkPBi8oJeN+NV8QD/7/MTmlB5qKUV1sg5BWRWL3Oqx9pfYhVa5rVNVbvAeD2MC49qQhGqovdfC5D71FW2uKgtqppSQTdnppeoIQDC/yMPpfTyv6jNEPlzr0DmbX0cpX4lNT9FwKKQk16ZYTqqlq478H6sAmMBEu2s354VDNNDevFVjwpZAuFy5BJxZ15ss8192/RRP1MEM6l7K0WhDF+hfSFcrcOGcqcy1Sqqfv2rZLMW0Uo/PWx0iWp7C5UY/z15bHzgkbyT9yKc/GXgIwirOMiJqxNSb5oNxQE3Y18tOLYxgNAWrqNA+RZKVjmrljSBQEHQDHE+E62L1lkbR2GAYuwgcM8KRDWOlVrOqX6hWNWdJ+IzQnjX3idoX2q/WhgJMdYzxXun3F7NAjL1UD8HY4Al8pONZBb1y33jlCxDFA96rh3EFswfPd72g175RvA2Kjt9aokU8TYaCWuHZvGLt4qcrXSjQAxQkAiOjBKhRnoUzkyS5oSpndxYmTJa1isUWN09Rpj+ENivBof6ifNEIPl1fHLExUbJyjtF3bQmdn/GhhPmnYxq7y0Q+0HwYDOzH5Idq+JRxgSSbcgJI+30/ZGTf6yMQjOvNTDFrglPJfpEmszg3m8teaSB2F0rjsGGo3ZGNFUEBEKSJsnX0XfQ9U3jAh6xxqeAi/TiVP+0CRad5hvuurVtr2jrIsSdidlo VsyiPt3u 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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: On Wed, Oct 22, 2025, Ackerley Tng wrote: > Ackerley Tng writes: > > Found another issue with KVM_CAP_MEMORY_ATTRIBUTES2. > > KVM_CAP_MEMORY_ATTRIBUTES2 was defined to do the same thing as > KVM_CAP_MEMORY_ATTRIBUTES, but that's wrong since > KVM_CAP_MEMORY_ATTRIBUTES2 should indicate the presence of > KVM_SET_MEMORY_ATTRIBUTES2 and struct kvm_memory_attributes2. No? If no attributes are supported, whether or not KVM_SET_MEMORY_ATTRIBUTES2 exists is largely irrelevant. We can even provide the same -ENOTTY errno by checking that _any_ attributes are supported, i.e. so that doing KVM_SET_MEMORY_ATTRIBUTES2 on KVM without any support whatsoever fails in the same way that KVM with code support but no attributes fails. In other words, I don't see why it can't do both. Even if we can't massage the right errno, I would much rather KVM_SET_MEMORY_ATTRIBUTES2 enumerate the set of supported attributes than simply '1'. E.g. we have no plans to support KVM_SET_MEMORY_ATTRIBUTES on guest_memfd, and so returning simply '1' creates an unwanted and unnecessary dependency. > @@ -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) Please use the same literal number, 0xd2, as #define KVM_SET_MEMORY_ATTRIBUTES _IOW(KVMIO, 0xd2, struct kvm_memory_attributes) The "final" ioctl number that userspace sees incorporates the directionality and the size of the struct, i.e. KVM_SET_MEMORY_ATTRIBUTES and KVM_SET_MEMORY_ATTRIBUTES2 are guaranteed to be distinct even if they both use 0xd2 as the "minor" number. > + > +struct kvm_memory_attributes2 { > + __u64 address; > + __u64 size; > + __u64 attributes; > + __u64 flags; > + __u64 reserved[4]; Maybe be paranoid and reserve 12 u64s?