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KVM: arm64: Enable support for guest_memfd backed memory

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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 <jthoughton@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-21-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Fuad Tabba 2025-07-29 15:54:51 -07:00 • committed by Paolo Bonzini
parent f4e740309e
commit 32e200bd6e
2 changed files with 8 additions and 0 deletions
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1
arch/arm64/kvm/Kconfig
View file

@ -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.

7
arch/arm64/kvm/mmu.c
View file

@ -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);