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AJvYcCUZ5XBcyKv6Q2ZNu0xtrxqTs9oPZTmVtq/9397cXjn54hu376uh6YDOxMGrjDjDlLzzGJhz3bMhgw==@kvack.org X-Gm-Message-State: AOJu0Yw/ehb7LU4UC8uVN+iSTvexvorpxEkqSaUbj3+EpEXtRGwHKjkR kl7jAWoUnXdJ+YwjjfWuRCyNBFn/3GxTAulN8OvPAs0R3x5pOF4D136e84noa7lwsfe4F/aYUND C+t0CQbBUp0p6zTii6i4BnjjJQI+Q1pCbWX3C X-Gm-Gg: ASbGncu9v/bTfHR9hlZUtattE/CzAiL94fY19pgye3bOGkUJNdFGc3xC+BQreEr7haT SelVviGpYFNxT6yBUAGC1HNiKBP8vuI1nMT6zqyZbG6++RmOFg4wIz3tByShM/o+DR2xwTEJ4Tf AsiVkecU3yi+fIgqxntelSRQV4MF0B+NSaP7E1agR+s55rPgvNLXYri0Y= X-Google-Smtp-Source: AGHT+IGihzOzWy8x+6Ja+LalRDd0k3+jQXGYbU3MHt0hkecArEO8Kjrf7J4KdbKoNVLOX2f2VTCUMWQSCZqQ6vCwIH4= X-Received: by 2002:a17:902:ce10:b0:216:2839:145 with SMTP id d9443c01a7336-22e3b071eb8mr1281395ad.1.1746508645256; Mon, 05 May 2025 22:17:25 -0700 (PDT) MIME-Version: 1.0 References: <386c1169-8292-43d1-846b-c50cbdc1bc65@redhat.com> <7e32aabe-c170-4cfc-99aa-f257d2a69364@redhat.com> In-Reply-To: From: Vishal Annapurve Date: Mon, 5 May 2025 22:17:12 -0700 X-Gm-Features: ATxdqUEzeS31T2q-e4VkgtgiiNIU1vS-masT4eZQygwiHzAZfHdNnbMPeJW7-MU Message-ID: Subject: Re: [PATCH v8 06/13] KVM: x86: Generalize private fault lookups to guest_memfd fault lookups To: Sean Christopherson Cc: David Hildenbrand , Ackerley Tng , 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, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: A52FF1C000A X-Stat-Signature: g9pzu43b7rr9s3ce1kt8woew1a3yja8j X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1746508646-110502 X-HE-Meta: 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 tGZHoz1k ldgU4GT3NmnIQvMz7ZlEJ/ZjL52hYuoIKl1njfCHj7OUzWHI3xHFvmlUvjqhiBrOmAN4O+fHrVwOUBDzBIC6wAWuYz0EYnFHBm/imXdAaVibk5ikrsOvcyYWTIB+JHW35bUM4Cke4ZlxmHoBdjdy/Qs+0+DJyw5ecDZp7GL4UstAoXHY64Jcoi8Z8XkOQ7LpYoSUJzBRjRSLCQm+eXxTX6He/G2/k6NXk+Pcmw46v+zk0Srci78L5PHdJXG0wYGzo7Ppn3fpc3MDFeQl/2aNjkfETUU/qR21VvHDbJDTZ2kp2K3wLZmQDK/asOqXjAWLSy6rxRJlnRierXEShsS6PlEEtwQ== 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 Mon, May 5, 2025 at 3:57=E2=80=AFPM Sean Christopherson wrote: > > ... > > And not worry about lpage_infor for the time being, until we actually d= o > > support larger pages. > > I don't want to completely punt on this, because if it gets messy, then I= want > to know now and have a solution in hand, not find out N months from now. > > That said, I don't expect it to be difficult. What we could punt on is > performance of the lookups, which is the real reason KVM maintains the ra= ther > expensive disallow_lpage array. > > And that said, memslots can only bind to one guest_memfd instance, so I d= on't > immediately see any reason why the guest_memfd ioctl() couldn't process t= he > slots that are bound to it. I.e. why not update KVM_LPAGE_MIXED_FLAG fro= m the > guest_memfd ioctl() instead of from KVM_SET_MEMORY_ATTRIBUTES? I am missing the point here to update KVM_LPAGE_MIXED_FLAG for the scenarios where in-place memory conversion will be supported with guest_memfd. As guest_memfd support for hugepages comes with the design that hugepages can't have mixed attributes. i.e. max_order returned by get_pfn will always have the same attributes for the folio range. Is your suggestion around using guest_memfd ioctl() to also toggle memory attributes for the scenarios where guest_memfd instance doesn't have in-place memory conversion feature enabled?