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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. > +/** > + * kvm_arch_supports_cacheable_pfnmap() - Determine whether hardware > + * supports cache management. > + * > + * Return: True if FWB and DIC is supported. I would elaborate some of the above commit message here so people understand why FWB and DIC are connected to this. Jason