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b=fB5u5dytoZH+98uvrjhJSL5NnZlmf5fZGsPzyhYrfyvhJwXiRppGmJoTmejP5T5Fz M5bhvSqL7jNYBfd44Mmd8LdzPSbjjn000TOHUGTfXPSvvD1K6sHJQheZgf9+2anLeE KQj+KiDnMsmWGniNFlZcWw4yp+uiBDungqoO4t1eBUfLMmYHda4BK70uoqKyb0GZlu 0fE/39irRV0Yhqn6CgM40sNBVNXmpzvmeSC/QK46uQ/PUoNFYSTAP1qunpWSnetVz8 0APFZjBhTQzg0DrLw6zK1CTVW6w3sXi7p0RCCw/fdSIa+0Ekybcr8xgpjtAE0ge5y3 l5gh4QLZuMQrQ== Message-ID: Date: Thu, 5 Mar 2026 20:08:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 08/15] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() To: "Kalyazin, Nikita" , "kvm@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "kvmarm@lists.linux.dev" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "bpf@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kernel@xen0n.name" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "loongarch@lists.linux.dev" Cc: "pbonzini@redhat.com" , "corbet@lwn.net" , "maz@kernel.org" , "oupton@kernel.org" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "seanjc@google.com" , "tglx@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "luto@kernel.org" , "peterz@infradead.org" , "willy@infradead.org" , "akpm@linux-foundation.org" , "lorenzo.stoakes@oracle.com" , "vbabka@suse.cz" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "martin.lau@linux.dev" , "eddyz87@gmail.com" , "song@kernel.org" , "yonghong.song@linux.dev" , "john.fastabend@gmail.com" , "kpsingh@kernel.org" , "sdf@fomichev.me" , "haoluo@google.com" , "jolsa@kernel.org" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "jannh@google.com" , "pfalcato@suse.de" , "shuah@kernel.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "kevin.brodsky@arm.com" , "ackerleytng@google.com" , "maobibo@loongson.cn" , "prsampat@amd.com" , "mlevitsk@redhat.com" , "jmattson@google.com" , "jthoughton@google.com" , "agordeev@linux.ibm.com" , "alex@ghiti.fr" , "aou@eecs.berkeley.edu" , "borntraeger@linux.ibm.com" , "chenhuacai@kernel.org" , "dev.jain@arm.com" , "gor@linux.ibm.com" , "hca@linux.ibm.com" , "palmer@dabbelt.com" , "pjw@kernel.org" , "shijie@os.amperecomputing.com" , "svens@linux.ibm.com" , "thuth@redhat.com" , "wyihan@google.com" , "yang@os.amperecomputing.com" , "Jonathan.Cameron@huawei.com" , "Liam.Howlett@oracle.com" , "urezki@gmail.com" , "zhengqi.arch@bytedance.com" , "gerald.schaefer@linux.ibm.com" , "jiayuan.chen@shopee.com" , "lenb@kernel.org" , "osalvador@suse.de" , "pavel@kernel.org" , "rafael@kernel.org" , "vannapurve@google.com" , "jackmanb@google.com" , "aneesh.kumar@kernel.org" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Cali, Marco" References: <20260126164445.11867-1-kalyazin@amazon.com> <20260126164445.11867-9-kalyazin@amazon.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 03E8B40018 X-Stat-Signature: prxrn49fi1w66wkhhiknx4bspkd9k6gw X-Rspam-User: X-HE-Tag: 1772737748-355033 X-HE-Meta: U2FsdGVkX18Tzcu9B8EvX/MKHEtDwPLLAr6pSvADzgGtabgPzXe29E2QV9gkIFeeG/fiXAbUM6eYstKGACDHVEssXsDuEAkeQynmSRbYDMwHd5oOJbjEGqstU6aLPIJ9y0kTQnCJSfbD/On2dtwRYFs/90n/irdRcadbQrktyYP6Rur4RNwZk3KU2jpZDCXRc0FR+SMeTMQT0m+8gS+vHPIhai5TuybK78brbPJdOpoJAYUCDPstvRdyo2MaCXzxqrhqYP7RKB5fZnV/IPr+wZZPb14Wle7b2rfS86rCXK8FFqR/EP9SUfdlmwskLu8al0gTj8Lwaf0JXQJ+qwV/6qqeXFHvwLxWrv6TZp46aCuOxZu9/gQ+fuj3V5L0mYlb3GzL3RTXMcFFYWT74H2k03qsYfzradM9MTZme98j+YfeaYn0JNi22Czno86h7vLtadNhZ9ALvXhlwGgEids5nu3SRhbfdVqF/C1XFenAeYZsDAE9Tq4dzcixUcLkuup5HRzYGRbVjsWH+H/mfJM13IxkCdtOc6e0bUb5iNIW9yFBwkCqU/t5cAzJNyPDFCAw+RusdIeAHuSoTmCRQme3Z29wu4KPBqIl9ag5fffV7F2pKmTcReOG7T3P3/5loCNZtXcXIfpwQtqxkAqtIeL2mfABEr+92BJs7owzs1BxXL3TEZMFCt3CdVea7uRoA3Q6bj07T4wbblLBaFalFbyKTvl0HhQTLOvMHJwu5We4yzDkhqbv+qRcshvPiM1Ui3P6jub3Ip2Syknhetwr8No1nWEaLz7+CepB5BcBpjJqGXX+PN0XeWaxc3WwrFnw1VjN81MzyDkY8zdmqzanwv947B9SPv5gc2pC8/JsSee8ExzEj5c/+OOxmMGE/zpeMQgtGONl4P/UpAPHGVrXDoZmLhhK2kSrw72kN8D5PtVYMvgu2R0Kp8i39+Q0gYu2/klTNjLh+mijARvDwRH1eNf COjggpzu e2TCuC5YufbzwkVPSnqu8Yk2HJjS67LJ0oXUYz+3zDUkV21lEERYq6cIh2OJZlYj5SyWfaN1x7fISu51RhDmpP3P4Z3RBaVFJha2mvbdGFfLigx2htZ7a3ByGlzmRsAImW4GgP0vBxF46X1WH4BMm/S7uAfpPhDsoK3u8J+7bYSwZuD0Acko0CglzCTaoNuw9CBkhoNOGDjBEBaBdt5VWZ4zSre515hsQhr3pvKPp81VRH3SBzNOCaOjEFOXOH9avscttHjk1Qee9VZx0xVmyCdG5lJ1ZU2ufT6j5BFKqhn2yZ8vmXZ10DeyLttFmIj8QRkwIxEvhjSwcEC434sWZ7O5nUDMDMubLAmvpaOJDW7GbiPfjjdmJhwijKdW4TrVaE5E+vEX399/pN1FsHH5j9NSWjegAUF9DMruEp1sYwjxqbmFkqTB2UgyucGvKAaiur2SARQ4Vt0oopMsBo+5pZqIv0Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/26/26 17:50, Kalyazin, Nikita wrote: > From: Patrick Roy > > Support for GUEST_MEMFD_FLAG_NO_DIRECT_MAP on arm64 depends on 1) direct > map manipulations at 4k granularity being possible, and 2) FEAT_S2FWB. > > 1) is met whenever the direct map is set up at 4k granularity (e.g. not > with huge/gigantic pages) at boottime, as due to ARM's > break-before-make semantics, breaking huge mappings into 4k mappings in > the direct map is not possible (BBM would require temporary invalidation > of the entire huge mapping, even if only a 4k subrange should be zapped, > which will probably crash the kernel). However, the current default for > rodata_full is true, which forces a 4k direct map. > > 2) is required to allow KVM to elide cache coherency operations when > installing stage 2 page tables, which require the direct map to be > entry for the newly mapped memory to be present (which it will not be, > as guest_memfd would have removed direct map entries in > kvm_gmem_get_pfn()). > > Cc: Will Deacon > Signed-off-by: Patrick Roy > Signed-off-by: Nikita Kalyazin > --- Reviewed-by: David Hildenbrand (Arm) -- Cheers, David