From: Fuad Tabba Date: Tue, 29 Jul 2025 22:54:51 +0000 (-0700) Subject: KVM: arm64: Enable support for guest_memfd backed memory X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=32e200bd6e4407c31aef0392be041274bfa3f20e;p=users%2Fhch%2Fmisc.git KVM: arm64: Enable support for guest_memfd backed memory Now that the infrastructure is in place, enable guest_memfd for arm64. * Select CONFIG_KVM_GUEST_MEMFD in KVM/arm64 Kconfig. * Enforce KVM_MEMSLOT_GMEM_ONLY for guest_memfd on arm64: Ensure that guest_memfd-backed memory slots on arm64 are only supported if they are intended for shared memory use cases (i.e., kvm_memslot_is_gmem_only() is true). This design reflects the current arm64 KVM ecosystem where guest_memfd is primarily being introduced for VMs that support shared memory. Reviewed-by: James Houghton Reviewed-by: Gavin Shan Reviewed-by: Marc Zyngier Acked-by: David Hildenbrand Signed-off-by: Fuad Tabba Signed-off-by: Sean Christopherson Message-ID: <20250729225455.670324-21-seanjc@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 713248f240e0..bff62e75d681 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -37,6 +37,7 @@ menuconfig KVM select HAVE_KVM_VCPU_RUN_PID_CHANGE select SCHED_INFO select GUEST_PERF_EVENTS if PERF_EVENTS + select KVM_GUEST_MEMFD help Support hosting virtualized guest machines. diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 5d73abc9bebc..a36426ccd9b5 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -2302,6 +2302,13 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, if ((new->base_gfn + new->npages) > (kvm_phys_size(&kvm->arch.mmu) >> PAGE_SHIFT)) return -EFAULT; + /* + * Only support guest_memfd backed memslots with mappable memory, since + * there aren't any CoCo VMs that support only private memory on arm64. + */ + if (kvm_slot_has_gmem(new) && !kvm_memslot_is_gmem_only(new)) + return -EINVAL; + hva = new->userspace_addr; reg_end = hva + (new->npages << PAGE_SHIFT);