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Tue, 15 Oct 2024 03:34:22 -0700 (PDT) MIME-Version: 1.0 References: <20241010085930.1546800-1-tabba@google.com> <20241010085930.1546800-7-tabba@google.com> In-Reply-To: From: Fuad Tabba Date: Tue, 15 Oct 2024 11:33:44 +0100 Message-ID: Subject: Re: [PATCH v3 06/11] KVM: guest_memfd: Add KVM capability to check if guest_memfd is host mappable To: Suzuki K Poulose Cc: 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, seanjc@google.com, 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, yu.c.zhang@linux.intel.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@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, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: C21D540006 X-Stat-Signature: g8p639bqsiqh76sem1f8cnwoi9u87h56 X-HE-Tag: 1728988453-23517 X-HE-Meta: U2FsdGVkX19nHGcDxycmfft3d9mX8qCRKXX+M1WJQYny/aIf7n5jVZVaLI3qEbdFaPIH/Gx1GYT8YxK7oJkFW6jcx4dKHeoNGNdWw+OpBfAr9hdK6fl+YpGNJKuZQ1so5KJhOc495iF1S+NRWC0yp13rCGP/tNhXxFiZH8/uTiMKVw3c+AG3b+eYsQrhS+o9lmvt9v5mw60/E75a7EllnB8EZ8r0zoRULfejr8gNHnGqQXBr8werDi2t4fODqZCLq1Sde4qRBqjBqG9DZXImFlomKPliLBHkF9XUtXRfsJn1QOekCzI3D1eqKgvibaOHZjKOBKzj0H52OqCDNbXI2o2RwPFwqwuHBSdtpPU27+uaDmw0TAkd4CW+PvgKD9BDE4NXPT8wCPaM3vidfjSpH2BuQA594N49izJIrNVi3QJh711C4zKvvsAEBVhOm7gdUMErXOTx2424/HRE3fsR93RkmJcfSaLpMKF8zQc5qhJGqcVxAWo+mR1vzYChqmi8c96dM3xLDOHn740OLvAvJIPFuwLAwHKxvrMLDYdenXE/5pWboO4Hn9MREbIOp0EKeLe3zHocdnWrW1s06nUWEJwiIk0ofBMYR2g4r5aDD/CIeJPk2QgYyyMbYI6tBEii7GBtnqHB5GAzT7p3N9kf9SNIhHNWthg45Dz7M5bO+Mi9JynEGrY83/MKashp80UbAwj7iNaDsTYqgm3LOBqoj46gRNUkzQoyJpD0Dz6Au4DOLbEZML38IAyTSOTqzWJSW6yavQRuL+ucbsf4xdvHIO3CP1Cu80TcVXKkyngQZDP/o3vowacj0IGPspCm/mdXih0nzPt9p5/LwxAUPHrLKnBKXMQNU6M4Y/daYk5z/Asrm7M61azSvLGQkXmex6KKaeF+dwrw6vDE8bGVevYOAifU7q1FhVUfE9xo4t/sYVqX7kuWVRFwDxS17IHyzeEY40O6aFGcBm4aKdc28n1 RU0o7Riu qAc9lfNye9Ad6RjKaMCO8ZsHBqv7JU5U3ic2XVi1FpmG8gNVeRyVJPp/gGwz7lTRhQJDjnqV9S04KzhuAILXVp37s1BZFvJBS5PY0q95/lGGjRP9F9MEhtQmcwgpVPKFtJRJ/UMVSkAmWTbxLO4niC4bKFwJfKOMCM1qr+0Bh9Zx99+We49AK86Dia+mD9VN+i3RJgoxTNnyT3wlsBarOAXD+/Kt/wQie8TMspiwZwtxtTQ1pZMO0TpAr1/Nho/5dzc46KW2Pp57u1rWqZDnpcrBPuIZVNOSKu33HduzOkt0R25lE4UkeqbrDtoJNJgoNZcjqtAjD9k+H9KucKMCpfmybzF8iYxgcdf2lHXegW3WxbwuZ3UYE5eE3ir4bdYQ47QIBt3qUbgY0E0k= 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: Hi Suzuki, On Tue, 15 Oct 2024 at 11:30, Suzuki K Poulose wro= te: > > Hi Fuad > > On 10/10/2024 09:59, Fuad Tabba wrote: > > Add the KVM capability KVM_CAP_GUEST_MEMFD_MAPPABLE, which is > > true if mapping guest memory is supported by the host. > > > > Signed-off-by: Fuad Tabba > > --- > > include/uapi/linux/kvm.h | 1 + > > virt/kvm/kvm_main.c | 4 ++++ > > 2 files changed, 5 insertions(+) > > > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > > index 637efc055145..2c6057bab71c 100644 > > --- a/include/uapi/linux/kvm.h > > +++ b/include/uapi/linux/kvm.h > > @@ -933,6 +933,7 @@ struct kvm_enable_cap { > > #define KVM_CAP_PRE_FAULT_MEMORY 236 > > #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237 > > #define KVM_CAP_X86_GUEST_MODE 238 > > +#define KVM_CAP_GUEST_MEMFD_MAPPABLE 239 > > > > struct kvm_irq_routing_irqchip { > > __u32 irqchip; > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index 77e6412034b9..c2ff09197795 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -5176,6 +5176,10 @@ static int kvm_vm_ioctl_check_extension_generic(= struct kvm *kvm, long arg) > > #ifdef CONFIG_KVM_PRIVATE_MEM > > case KVM_CAP_GUEST_MEMFD: > > return !kvm || kvm_arch_has_private_mem(kvm); > > +#endif > > +#ifdef CONFIG_KVM_GMEM_MAPPABLE > > + case KVM_CAP_GUEST_MEMFD_MAPPABLE: > > + return !kvm || kvm_arch_has_private_mem(kvm); > > minor nit: Keying this on whether the "kvm" instance has private mem > may not be flexible enough to support other types of CC guest that > may use guestmem, but not "mappable" memory. e.g. CCA may not > support "mappable", unless we have a way to explicitly pass down > "you can map a shared page from the guest_memfd, but it is not > sharable in place". > > We could solve it when we get there, but it might be worth > considering. I did consider that, but I assumed that the configuration option would be sufficient. Otherwise, we could make it dependent on the VM type. Cheers, /fuad > Suzuki > > > > > > #endif > > default: > > break; > > IMPORTANT NOTICE: The contents of this email and any attachments are conf= idential and may also be privileged. If you are not the intended recipient,= please notify the sender immediately and do not disclose the contents to a= ny other person, use it for any purpose, or store or copy the information i= n any medium. Thank you.