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suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, shahuang@redhat.com, lpieralisi@kernel.org, david@redhat.com, ddutile@redhat.com, seanjc@google.com, 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 Subject: Re: [PATCH v9 4/6] KVM: arm64: New function to determine hardware cache management support Message-ID: <20250704134740.GG1410929@nvidia.com> References: 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 wrkzyL12 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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 > --- > arch/arm64/kvm/mmu.c | 23 +++++++++++++++++++++++ > include/linux/kvm_host.h | 2 ++ > virt/kvm/kvm_main.c | 5 +++++ > 3 files changed, 30 insertions(+) Reviewed-by: Jason Gunthorpe Jason