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[2003:d8:2f2c:5500:988:23f9:faa0:7232]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454a997ae2esm56138585e9.9.2025.07.04.07.10.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Jul 2025 07:10:32 -0700 (PDT) Message-ID: <7ccee3be-6438-462d-8dce-efa58238f28d@redhat.com> Date: Fri, 4 Jul 2025 16:10:30 +0200 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 4/6] KVM: arm64: New function to determine hardware cache management support To: ankita@nvidia.com, jgg@nvidia.com, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, shahuang@redhat.com, lpieralisi@kernel.org, ddutile@redhat.com, seanjc@google.com Cc: aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, kjaju@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, zhiw@nvidia.com, mochs@nvidia.com, udhoke@nvidia.com, dnigam@nvidia.com, alex.williamson@redhat.com, sebastianene@google.com, coltonlewis@google.com, kevin.tian@intel.com, yi.l.liu@intel.com, ardb@kernel.org, akpm@linux-foundation.org, gshan@redhat.com, linux-mm@kvack.org, tabba@google.com, qperret@google.com, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maobibo@loongson.cn References: <20250621042111.3992-1-ankita@nvidia.com> <20250621042111.3992-5-ankita@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21.06.25 06:21, ankita@nvidia.com wrote: > From: Ankit Agrawal > > VM_PFNMAP VMA's are allowed to contain PTE's which point to physical > addresses that does not have a struct page and may not be in the kernel > direct map. > > However ARM64 KVM relies on a simple conversion from physaddr to a > kernel virtual address when it does cache maintenance as the CMO > instructions work on virtual addresses. This simple approach does not > work for physical addresses from VM_PFNMAP since those addresses may > not have a kernel virtual address, or it may be difficult to find it. > > Fortunately if the ARM64 CPU has two features, S2FWB and CACHE DIC, > then KVM no longer needs to do cache flushing and NOP's all the > CMOs. This has the effect of no longer requiring a KVA for addresses > mapped into the S2. > > Add a new function, kvm_arch_supports_cacheable_pfnmap(), to report > this capability. From a core prespective it means the arch can accept > a cachable VM_PFNMAP as a memslot. From an ARM64 perspective it means > that no KVA is required. > > CC: Jason Gunthorpe > CC: David Hildenbrand > CC: Donald Dutile > Reviewed-by: Catalin Marinas > Signed-off-by: Ankit Agrawal > --- Reviewed-by: David Hildenbrand -- Cheers, David / dhildenb