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[2003:cb:c705:7600:62cc:24c1:9dbe:a2f5]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4316069e1c9sm1407195e9.25.2024.10.17.10.11.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Oct 2024 10:11:47 -0700 (PDT) Message-ID: Date: Thu, 17 Oct 2024 19:11:46 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 26/39] KVM: guest_memfd: Track faultability within a struct kvm_gmem_private To: Jason Gunthorpe , Peter Xu Cc: Ackerley Tng , tabba@google.com, quic_eberman@quicinc.com, roypat@amazon.co.uk, rientjes@google.com, fvdl@google.com, jthoughton@google.com, seanjc@google.com, pbonzini@redhat.com, zhiquan1.li@intel.com, fan.du@intel.com, jun.miao@intel.com, isaku.yamahata@intel.com, muchun.song@linux.dev, erdemaktas@google.com, vannapurve@google.com, qperret@google.com, jhubbard@nvidia.com, willy@infradead.org, shuah@kernel.org, brauner@kernel.org, bfoster@redhat.com, kent.overstreet@linux.dev, pvorel@suse.cz, rppt@kernel.org, richard.weiyang@gmail.com, anup@brainfault.org, haibo1.xu@intel.com, ajones@ventanamicro.com, vkuznets@redhat.com, maciej.wieczor-retman@intel.com, pgonda@google.com, oliver.upton@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org References: <1d243dde-2ddf-4875-890d-e6bb47931e40@redhat.com> <20241016225157.GQ3559746@nvidia.com> <20241016235424.GU3559746@nvidia.com> <20241017164713.GF3559746@nvidia.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.10.24 18:47, Jason Gunthorpe wrote: > On Thu, Oct 17, 2024 at 10:58:29AM -0400, Peter Xu wrote: > >> My question was more torwards whether gmemfd could still expose the >> possibility to be used in VA forms to other modules that may not support >> fd+offsets yet. > > I keep hearing they don't want to support page pinning on a guestmemfd > mapping, so VA based paths could not work. For shared pages it absolutely must work. That's what I keep hearing :) > >> I think as long as we can provide gmemfd VMAs like what this series >> provides, it sounds possible to reuse the old VA interfaces before the CoCo >> interfaces are ready, so that people can already start leveraging gmemfd >> backing pages. > > And you definitely can't get the private pages out of the VA interface > because all the VMA PTEs of private pages are non-present by definition. Agreed. -- Cheers, David / dhildenb