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[2003:d8:2f45:5500:8267:647f:4209:dedd]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442cd32f24fsm83677725e9.16.2025.05.09.15.29.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 May 2025 15:29:22 -0700 (PDT) Message-ID: Date: Sat, 10 May 2025 00:29:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 06/13] KVM: x86: Generalize private fault lookups to guest_memfd fault lookups To: James Houghton , Ackerley Tng Cc: Sean Christopherson , Vishal Annapurve , Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, peterx@redhat.com, pankaj.gupta@amd.com References: <386c1169-8292-43d1-846b-c50cbdc1bc65@redhat.com> <7e32aabe-c170-4cfc-99aa-f257d2a69364@redhat.com> <39ea3946-6683-462e-af5d-fe7d28ab7d00@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: ctaq65csmckdsf6yi7iku6zs8a4sm1wg X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8637D40003 X-Rspam-User: X-HE-Tag: 1746829766-118126 X-HE-Meta: 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 qnUXmoXA jtswNnjhYiSmmzUg/9Ag2yQSIZfuKWX3qhaeA84wxZHThVVghPm3zKaMa9cN+IKe2wqIFROpLY2GSA5w8/hyhoS5HoZlxR3TzP3C4TmzKHX6qnCzECdbbBWnDb/8yeB83E+fw1sFLOk4QeCWY8tqpAPm9CN4u4iU+G2m+dbSUTLEagCJUqqHf6q+ZrpncxBdhOg3Z 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 09.05.25 23:04, James Houghton wrote: > On Tue, May 6, 2025 at 1:47 PM Ackerley Tng wrote: >> From here [1], these changes will make it to v9 >> >> + kvm_max_private_mapping_level renaming to kvm_max_gmem_mapping_level >> + kvm_mmu_faultin_pfn_private renaming to kvm_mmu_faultin_pfn_gmem >> >>> Only kvm_mmu_hugepage_adjust() must be taught to not rely on >>> fault->is_private. >>> >> >> I think fault->is_private should contribute to determining the max >> mapping level. >> >> By the time kvm_mmu_hugepage_adjust() is called, >> >> * For Coco VMs using guest_memfd only for private memory, >> * fault->is_private would have been checked to align with >> kvm->mem_attr_array, so >> * For Coco VMs using guest_memfd for both private/shared memory, >> * fault->is_private would have been checked to align with >> guest_memfd's shareability >> * For non-Coco VMs using guest_memfd >> * fault->is_private would be false > > I'm not sure exactly which thread to respond to, but it seems like the > idea now is to have a *VM* flag determine if shared faults use gmem or > use the user mappings. It seems more natural for that to be a property > of the memslot / a *memslot* flag. I think that's exactly what we discussed in the last meetings. The guest_memfd flag essentially defines that. So it's not strictly a memslot flag but rather a guest_memfd flag, and the memslot is configured with that guest_memfd, inheriting that flag. There might be a VM capability, whether it supports creation of these new guest_memfds (iow, guest_memfd understands the new flag). -- Cheers, David / dhildenb