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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.googlemail.com with ESMTPSA id z5-20020a509e05000000b0052e1783ab25sm1584481ede.70.2023.11.01.15.28.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Nov 2023 15:28:34 -0700 (PDT) Message-ID: <4ca2253d-276f-43c5-8e9f-0ded5d5b2779@redhat.com> Date: Wed, 1 Nov 2023 23:28:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 17/35] KVM: Add transparent hugepage support for dedicated guest memory To: Sean Christopherson References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-18-seanjc@google.com> <7c0844d8-6f97-4904-a140-abeabeb552c1@intel.com> <92ba7ddd-2bc8-4a8d-bd67-d6614b21914f@intel.com> From: Paolo Bonzini Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chao Peng , linux-riscv@lists.infradead.org, Isaku Yamahata , Marc Zyngier , Huacai Chen , Xiaoyao Li , "Matthew Wilcox \(Oracle\)" , Wang , Fuad Tabba , Yu Zhang , Maciej Szmigiero , Albert Ou , Vlastimil Babka , Michael Roth , Ackerley Tng , Alexander Viro , Paul Walmsley , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, =?UTF-8?B?TWlja2HDq2wgU2FsYcO8?= =?UTF-8?Q?n?= , Isaku Yamahata , Christian Brauner , Quentin Perret , Anup Patel , linux-mips@vger.kernel.org, Oliver Upton , David Matlack , Jarkko Sakkinen , Palmer Dabbelt , "Kirill A . Shutemov" , kvm-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, Liam Merwick , Andrew Morton , Vishal Annapurve , linuxppc-dev@lists.ozlabs.org, Xu Yilun , Anish Moorthy Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11/1/23 17:36, Sean Christopherson wrote: >>> "Allow" isn't perfect, e.g. I would much prefer a straight KVM_GUEST_MEMFD_USE_HUGEPAGES >>> or KVM_GUEST_MEMFD_HUGEPAGES flag, but I wanted the name to convey that KVM doesn't >>> (yet) guarantee hugepages. I.e. KVM_GUEST_MEMFD_ALLOW_HUGEPAGE is stronger than >>> a hint, but weaker than a requirement. And if/when KVM supports a dedicated memory >>> pool of some kind, then we can add KVM_GUEST_MEMFD_REQUIRE_HUGEPAGE. >> I think that the current patch is fine, but I will adjust it to always >> allow the flag, and to make the size check even if !CONFIG_TRANSPARENT_HUGEPAGE. >> If hugepages are not guaranteed, and (theoretically) you could have no >> hugepage at all in the result, it's okay to get this result even if THP is not >> available in the kernel. > Can you post a fixup patch? It's not clear to me exactly what behavior you intend > to end up with. Sure, just this: diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 7d1a33c2ad42..34fd070e03d9 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -430,10 +430,7 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) { loff_t size = args->size; u64 flags = args->flags; - u64 valid_flags = 0; - - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) - valid_flags |= KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; + u64 valid_flags = KVM_GUEST_MEMFD_ALLOW_HUGEPAGE; if (flags & ~valid_flags) return -EINVAL; @@ -441,11 +438,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) if (size < 0 || !PAGE_ALIGNED(size)) return -EINVAL; -#ifdef CONFIG_TRANSPARENT_HUGEPAGE if ((flags & KVM_GUEST_MEMFD_ALLOW_HUGEPAGE) && !IS_ALIGNED(size, HPAGE_PMD_SIZE)) return -EINVAL; -#endif return __kvm_gmem_create(kvm, size, flags); } Paolo