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[2003:cb:c705:7600:62cc:24c1:9dbe:a2f5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d7fbf82b1sm7554576f8f.72.2024.10.17.07.56.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Oct 2024 07:56:31 -0700 (PDT) Message-ID: <98eacabd-3465-4f5d-b045-8e8595d68676@redhat.com> Date: Thu, 17 Oct 2024 16:56:30 +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: Peter Xu , Jason Gunthorpe 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> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: n1pdkqq86rnzd6q37if74ohd9dbqcoeb X-Rspamd-Queue-Id: 2AEBB180011 X-Rspamd-Server: rspam11 X-HE-Tag: 1729176989-871814 X-HE-Meta: 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 f1xmSGMg 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 01:49, Peter Xu wrote: > On Wed, Oct 16, 2024 at 07:51:57PM -0300, Jason Gunthorpe wrote: >> On Wed, Oct 16, 2024 at 04:16:17PM -0400, Peter Xu wrote: >>> >>> Is there chance that when !CoCo will be supported, then external modules >>> (e.g. VFIO) can reuse the old user mappings, just like before gmemfd? >>> >>> To support CoCo, I understand gmem+offset is required all over the places. >>> However in a non-CoCo context, I wonder whether the other modules are >>> required to stick with gmem+offset, or they can reuse the old VA ways, >>> because how it works can fundamentally be the same as before, except that >>> the folios now will be managed by gmemfd. >> >> My intention with iommufd was to see fd + offest as the "new" way >> to refer to all guest memory and discourage people from using VMA >> handles. > > Does it mean anonymous memory guests will not be supported at all for > iommufd? > > Indeed it's very rare now, lose quite some flexibility (v.s. fd based), and > I can't think of a lot besides some default configs or KSM users (which I > would expect rare), but still I wonder there're other use cases that people > would still need to stick with anon, hence fd isn't around. Not sure I completely understand the question, but for most VMs out there I expect an anonymous memory to remain the default memory backing. Regarding users of iommufd, I have absolutely no clue :) -- Cheers, David / dhildenb