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Thu, 20 Jul 2023 08:14:49 -0700 (PDT) Date: Thu, 20 Jul 2023 08:14:47 -0700 In-Reply-To: <83eb5c50-7287-7845-ffc3-a7c58e638ea5@intel.com> Mime-Version: 1.0 References: <20230718234512.1690985-1-seanjc@google.com> <20230718234512.1690985-13-seanjc@google.com> <83eb5c50-7287-7845-ffc3-a7c58e638ea5@intel.com> Message-ID: Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Xiaoyao Li Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , "Matthew Wilcox (Oracle)" , Andrew Morton , Paul Moore , James Morris , "Serge E. Hallyn" , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Chao Peng , Fuad Tabba , Jarkko Sakkinen , Yu Zhang , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , Vlastimil Babka , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 816CF40025 X-Stat-Signature: dfd94kppeyd3k4esqkqipidyhwaxnscu X-Rspam-User: X-HE-Tag: 1689866090-926077 X-HE-Meta: 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 M3exMW99 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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: On Thu, Jul 20, 2023, Xiaoyao Li wrote: > On 7/19/2023 7:44 AM, Sean Christopherson wrote: > > @@ -5134,6 +5167,16 @@ static long kvm_vm_ioctl(struct file *filp, > > case KVM_GET_STATS_FD: > > r = kvm_vm_ioctl_get_stats_fd(kvm); > > break; > > + case KVM_CREATE_GUEST_MEMFD: { > > + struct kvm_create_guest_memfd guest_memfd; > > + > > + r = -EFAULT; > > + if (copy_from_user(&guest_memfd, argp, sizeof(guest_memfd))) > > + goto out; > > + > > + r = kvm_gmem_create(kvm, &guest_memfd); > > + break; > > + } > > Does it need a new CAP to indicate the support of guest_memfd? Yeah, I meant to add that to the TODO list and forgot (obviously). > This is patch series introduces 3 new CAPs and it seems any one of them can > serve as the indicator of guest_memfd. > > +#define KVM_CAP_USER_MEMORY2 230 > +#define KVM_CAP_MEMORY_ATTRIBUTES 231 > +#define KVM_CAP_VM_TYPES 232 The number of new caps being added is the main why I didn't just add another one. On the other hand, we have room for a few billion caps, so one more isn't a big deal. So yeah, KVM_CAP_GUEST_MEMFD is probably the way to go.