From: Fuad Tabba <tabba@google.com>
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>
---
arch/arm64/kvm/Kconfig | 1 +
arch/arm64/kvm/mmu.c | 7 +++++++
2 files changed, 8 insertions(+)
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 8c82df80a835..85559b8a0845 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -2276,6 +2276,13 @@ 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);
--
2.50.1.552.g942d659e1b-goog