Enable host userspace mmap support for guest_memfd-backed memory on arm64. This change provides arm64 with the capability to map guest memory at the host directly from guest_memfd: * Define kvm_arch_supports_gmem_mmap() for arm64: The kvm_arch_supports_gmem_mmap() macro is defined for arm64 to be true if CONFIG_KVM_GMEM_SUPPORTS_MMAP is enabled. For existing arm64 KVM VM types that support guest_memfd, this enables them to use guest_memfd with host userspace mappings. This provides a consistent behavior as there are currently no arm64 CoCo VMs that rely on guest_memfd solely for private, non-mappable memory. Future arm64 VM types can override or restrict this behavior via the kvm_arch_supports_gmem_mmap() hook if needed. * Select CONFIG_KVM_GMEM_SUPPORTS_MMAP in arm64 Kconfig. * Enforce KVM_MEMSLOT_GMEM_ONLY for guest_memfd on arm64: Checks are added to ensure that if guest_memfd is enabled on arm64, KVM_GMEM_SUPPORTS_MMAP must also be enabled. This means guest_memfd-backed memory slots on arm64 are currently 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@xxxxxxxxxx> Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx> --- arch/arm64/include/asm/kvm_host.h | 4 ++++ arch/arm64/kvm/Kconfig | 2 ++ arch/arm64/kvm/mmu.c | 7 +++++++ 3 files changed, 13 insertions(+) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 3e41a880b062..63f7827cfa1b 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1674,5 +1674,9 @@ void compute_fgu(struct kvm *kvm, enum fgt_group_id fgt); void get_reg_fixed_bits(struct kvm *kvm, enum vcpu_sysreg reg, u64 *res0, u64 *res1); void check_feature_map(void); +#ifdef CONFIG_KVM_GMEM +#define kvm_arch_supports_gmem(kvm) true +#define kvm_arch_supports_gmem_mmap(kvm) IS_ENABLED(CONFIG_KVM_GMEM_SUPPORTS_MMAP) +#endif #endif /* __ARM64_KVM_HOST_H__ */ diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 713248f240e0..323b46b7c82f 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -37,6 +37,8 @@ menuconfig KVM select HAVE_KVM_VCPU_RUN_PID_CHANGE select SCHED_INFO select GUEST_PERF_EVENTS if PERF_EVENTS + select KVM_GMEM + select KVM_GMEM_SUPPORTS_MMAP 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); -- 2.50.0.727.gbf7dc18ff4-goog
