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Fri, 10 Apr 2026 15:19:24 +0000 Received: from EX19D027UEC003.ant.amazon.com ([fe80::887f:519b:ba73:21d]) by EX19D027UEC003.ant.amazon.com ([fe80::887f:519b:ba73:21d%3]) with mapi id 15.02.2562.037; Fri, 10 Apr 2026 15:19:24 +0000 From: "Kalyazin, Nikita" To: "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" , "linux-pm@vger.kernel.org" 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" , "david@kernel.org" , "lorenzo.stoakes@oracle.com" , "vbabka@kernel.org" , "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" , "skhan@linuxfoundation.org" , "riel@surriel.com" , "ryan.roberts@arm.com" , "jgross@suse.com" , "yu-cheng.yu@intel.com" , "kas@kernel.org" , "coxu@redhat.com" , "ackerleytng@google.com" , "yosry@kernel.org" , "ajones@ventanamicro.com" , "maobibo@loongson.cn" , "tabba@google.com" , "prsampat@amd.com" , "wu.fei9@sanechips.com.cn" , "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" , "baolu.lu@linux.intel.com" , "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" , "yang@os.amperecomputing.com" , "Liam.Howlett@oracle.com" , "urezki@gmail.com" , "zhengqi.arch@bytedance.com" , "gerald.schaefer@linux.ibm.com" , "jiayuan.chen@shopee.com" , "lenb@kernel.org" , "pavel@kernel.org" , "rafael@kernel.org" , "yangyicong@hisilicon.com" , "vannapurve@google.com" , "jackmanb@google.com" , "patrick.roy@linux.dev" , "Thomson, Jack" , "Itazuri, Takahiro" , "Manwaring, Derek" , "Kalyazin, Nikita" Subject: [PATCH v12 09/16] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() Thread-Topic: [PATCH v12 09/16] KVM: arm64: define kvm_arch_gmem_supports_no_direct_map() Thread-Index: AQHcyP1pqKPFicKVfkONXJiuCe9SiA== Date: Fri, 10 Apr 2026 15:19:24 +0000 Message-ID: <20260410151746.61150-10-kalyazin@amazon.com> References: <20260410151746.61150-1-kalyazin@amazon.com> In-Reply-To: <20260410151746.61150-1-kalyazin@amazon.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.19.103.116] MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260410_081927_573709_7D21BA7C X-CRM114-Status: UNSURE ( 9.60 ) X-CRM114-Notice: Please train this message. X-Mailman-Approved-At: Sun, 19 Apr 2026 16:02:05 -0700 X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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 Reviewed-by: David Hildenbrand (Arm) Signed-off-by: Nikita Kalyazin --- arch/arm64/include/asm/kvm_host.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 70cb9cfd760a..fbdd43e7e94e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -1682,6 +1683,18 @@ static __always_inline enum fgt_group_id __fgt_reg_to_group_id(enum vcpu_sysreg \ p; \ }) +#ifdef CONFIG_KVM_GUEST_MEMFD +static inline bool kvm_arch_gmem_supports_no_direct_map(struct kvm *kvm) +{ + /* + * Without FWB, direct map access is needed in kvm_pgtable_stage2_map(), + * as it calls dcache_clean_inval_poc(). + */ + return can_set_direct_map() && cpus_have_final_cap(ARM64_HAS_STAGE2_FWB); +} +#define kvm_arch_gmem_supports_no_direct_map kvm_arch_gmem_supports_no_direct_map +#endif /* CONFIG_KVM_GUEST_MEMFD */ + long kvm_get_cap_for_kvm_ioctl(unsigned int ioctl, long *ext); -- 2.50.1 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv