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Fri, 17 Jan 2025 08:58:35 -0800 (PST) Message-ID: <23fa05f8-ea30-4261-91d8-b34fc678c4de@redhat.com> Date: Fri, 17 Jan 2025 17:58:29 +0100 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 v2 1/1] KVM: arm64: Allow cacheable stage 2 mapping using VMA flags To: Jason Gunthorpe , Catalin Marinas Cc: Ankit Agrawal , "maz@kernel.org" , "oliver.upton@linux.dev" , "joey.gouly@arm.com" , "suzuki.poulose@arm.com" , "yuzenghui@huawei.com" , "will@kernel.org" , "ryan.roberts@arm.com" , "shahuang@redhat.com" , "lpieralisi@kernel.org" , Aniket Agashe , Neo Jia , Kirti Wankhede , "Tarun Gupta (SW-GPU)" , Vikram Sethi , Andy Currid , Alistair Popple , John Hubbard , Dan Williams , Zhi Wang , Matt Ochs , Uday Dhoke , Dheeraj Nigam , "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" , "kvmarm@lists.linux.dev" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" References: <20250106165159.GJ5556@nvidia.com> <20250113162749.GN5556@nvidia.com> <0743193c-80a0-4ef8-9cd7-cb732f3761ab@redhat.com> <20250114133145.GA5556@nvidia.com> <20250115143213.GQ5556@nvidia.com> <20250117140050.GC5556@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >> I don't see how VM_PFNMAP alone can tell us anything about the >> access properties supported by a device address range. Either way, >> it's the driver setting vm_page_prot or some VM_* flag. KVM has no >> clue, it's just a memory slot. > > I think David's point about VM_PFNMAP was to avoid some of the > pfn_valid() logic. If we get VM_PFNMAP we just assume it is non-struct > page and follow the VMA's pgprot. Exactly what I meant. If we only expect DEVICE stuff in VM_PFNMAP, then we can limit all the weirdness (and figuring out what todo using pgprot etc) to exactly that. VM_IO without VM_PFNMAP might be interesting; not sure if we even want to support that here. -- Cheers, David / dhildenb