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AJvYcCXYV8+V9I1bMRwjiOjavNdtLNWVC3jzbmISa4AKw6zgSWkp0Kpp9U8xfmjj9ND+5y25g54lkuAgpw==@kvack.org X-Gm-Message-State: AOJu0YxRn21HOcvrfFWg1gnyK0OYYHn/JThZS7kDcL9Dh5GyPQQziOQR bTs5qQBGBrm0vj9IV1l0Cb7Cr8PUZMCVglo8/HU/JuxlSorAC2F0vYGGzeoKDypiYvgpiCGV1JP 8/00lukiGcG420gyQKbchI2qaNUYvKpoX7iS+ X-Gm-Gg: ASbGncscfMu8bUY2aQYULp8n8lEDDp1S3VYQ/CsBwV4KxNLa9tBiLWfF9Ae57xODwRW OyQ3yzuKqqoMHlCDE7nLKX5ZuN58ks7QovvyTd+gYr2icFu7wLMJXDIMrjhZXpjmzxz+vVSGEMV SLWaFLI0vcs14SRg9bkeUZL/VQ5K2ZUEdoLwD0xslC5+sWcPrblRIKZIUUQS7bMAw= X-Google-Smtp-Source: AGHT+IFlK+yC5lgOv11bmhC+bVjGZ3bX7IBXVoaQbIwYaU7KQJR4oxZrRbUoNAVwfkFpzhpAbBPeDKRzVihbwxVGZvo= X-Received: by 2002:a05:690c:6181:b0:6fb:b1dd:a00d with SMTP id 00721157ae682-70a3fb0f629mr70163017b3.30.1746824705902; Fri, 09 May 2025 14:05:05 -0700 (PDT) MIME-Version: 1.0 References: <386c1169-8292-43d1-846b-c50cbdc1bc65@redhat.com> <7e32aabe-c170-4cfc-99aa-f257d2a69364@redhat.com> <39ea3946-6683-462e-af5d-fe7d28ab7d00@redhat.com> In-Reply-To: From: James Houghton Date: Fri, 9 May 2025 14:04:29 -0700 X-Gm-Features: AX0GCFuCWbYwnP1AwYVXy2ElKQAoD2B95TUeHHXsalKtgwvYczk2esQtcrZ5wXs Message-ID: Subject: Re: [PATCH v8 06/13] KVM: x86: Generalize private fault lookups to guest_memfd fault lookups To: Ackerley Tng Cc: David Hildenbrand , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 303A31C0012 X-Stat-Signature: qzm6x9q4syfsxomizib5jtayg1cba87w X-Rspam-User: X-HE-Tag: 1746824706-249185 X-HE-Meta: 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 P83ZzYpl Mvit7OR017jYf+q/n4VXoQgyG23b6HDv+wWLSamL8Tmu/eTRfxSmEkMp6QqDAlUQ360SJ5MZh+zDeSG6BqNNDHlMQ3O5/t8MCw2z4cc48Ne4Pj3mp04Gz4DBy3AZOQ/2yN/h1wz3Sjt1MWs9cAjwaXl9rDTHPXGPZQV0GU5MVNMEv5EmRfdtdqdXIhaUmQAG2WuqrmSpSEub0EHITrkab4+E8SGTZMwjNWEIaZj4wMRx5VE5ADHKNX2bh6ohjsUNnXUbyNc7zeaderE0iu7Lba6PyZ8VLJ2tUFGjC+3EKDXJf5fcLovxCfku+VzC8zZL9AalgpQWEzQrKiDdMVrzVyw6O+Wajet3EZ2oO9hsicGviG25LeP5d5FIe1MXWoDQXNZV6eR47ggCQb69Y83LSGEwfuCSy7b2pzmro 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 Tue, May 6, 2025 at 1:47=E2=80=AFPM 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. Sean, Fuad, what do you think? I don't see any downsides, and it seems strictly more flexible. > [1] https://lore.kernel.org/all/20250430165655.605595-7-tabba@google.com/ > [2] https://lore.kernel.org/all/diqz1pt1sfw8.fsf@ackerleytng-ctop.c.googl= ers.com/