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AJvYcCXX3XSWeOz9LuUcaIGu8cBNKXbYPpeB+QAH77rLkMWaMn8oJg7MJc6HwM5a3briLJwWoSIm4Lxagg==@kvack.org X-Gm-Message-State: AOJu0Yxyj+Vc6Z6LG7JMITapkdleOaGK/anSCF0uKk8SAZ/yoRf8o+l+ PxvYC3vRnRE4eSCBexIO3xyN8+ZrSIOhzOqedQ7q2GDyDe2mitieyxuOKg6JpQinAaA3anf4G7A GqFe/Sw== X-Google-Smtp-Source: AGHT+IHbAz/eKQpxYLnv3UzRDiNfzFQyWZ03GI8G+wp5sD4kBBYyUq+g8Y0WEpcjXQKRT5uv4bipYXGp6JQ= X-Received: from pjbsf1.prod.google.com ([2002:a17:90b:51c1:b0:2e0:915d:d594]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:514e:b0:312:25dd:1c86 with SMTP id 98e67ed59e1d1-31e778f7879mr4767541a91.18.1753464276017; Fri, 25 Jul 2025 10:24:36 -0700 (PDT) Date: Fri, 25 Jul 2025 10:24:34 -0700 In-Reply-To: Mime-Version: 1.0 References: <20250723104714.1674617-1-tabba@google.com> <20250723104714.1674617-15-tabba@google.com> <1ff6a90a-3e03-4104-9833-4b07bb84831f@intel.com> Message-ID: Subject: Re: [PATCH v16 14/22] KVM: x86/mmu: Enforce guest_memfd's max order when recovering hugepages From: Sean Christopherson To: Ackerley Tng Cc: Xiaoyao Li , Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev, 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, 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, vannapurve@google.com, mail@maciej.szmigiero.name, david@redhat.com, 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, ira.weiny@intel.com Content-Type: text/plain; charset="us-ascii" X-Rspamd-Queue-Id: 45E71A0002 X-Stat-Signature: 8bb1ksqaq4ugdo8p6umf9x9jq5qrwngh X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1753464277-557580 X-HE-Meta: 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 6PN9D2MP 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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 Fri, Jul 25, 2025, Sean Christopherson wrote: > On Thu, Jul 24, 2025, Ackerley Tng wrote: > I also don't want to effectively speculatively add kvm_gmem_mapping_order() or > expand kvm_gmem_get_pfn(), e.g. to say "no create", so what if we just do this? > > /* For faults, use the gmem information that was resolved earlier. */ > if (fault) { > pfn = fault->pfn; > max_level = fault->max_level; > } else { > /* TODO: Call into guest_memfd once hugepages are supported. */ Aha! Even better, we can full on WARN: WARN_ONCE(1, "Get pfn+order from guest_memfd"); Because guest_memfd doesn't yet support dirty logging: /* Dirty logging private memory is not currently supported. */ if (mem->flags & KVM_MEM_GUEST_MEMFD) valid_flags &= ~KVM_MEM_LOG_DIRTY_PAGES; which kills off the kvm_mmu_recover_huge_pages() call from kvm_mmu_slot_apply_flags(). And if KVM ever supports in-place recover for kvm_recover_nx_huge_pages() (which is doubtful given that mitigation shouldn't be required going forward), lack of hugepage support means any guest_memfd-based shadow page can't be a possible NX hugepage.