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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 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 Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 7661C80006 X-Stat-Signature: tnfnsyun3sb5u6g7wu5sopphhbm4gjyw X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1729185092-310843 X-HE-Meta: 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 6QDDu4Gy 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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