From: Jack Thomson <[email protected]> Add kvm_arch_vcpu_pre_fault_memory() for arm64. The implementation hands off the stage-2 faulting logic to either gmem_abort() or user_mem_abort().
Add an optional page_size output parameter to user_mem_abort() to return the VMA page size, which is needed when pre-faulting. Update the documentation to clarify x86 specific behaviour. Signed-off-by: Jack Thomson <[email protected]> --- Documentation/virt/kvm/api.rst | 3 +- arch/arm64/kvm/Kconfig | 1 + arch/arm64/kvm/arm.c | 1 + arch/arm64/kvm/mmu.c | 79 ++++++++++++++++++++++++++++++++-- 4 files changed, 79 insertions(+), 5 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 01a3abef8abb..44cfd9e736bb 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6493,7 +6493,8 @@ Errors: KVM_PRE_FAULT_MEMORY populates KVM's stage-2 page tables used to map memory for the current vCPU state. KVM maps memory as if the vCPU generated a stage-2 read page fault, e.g. faults in memory as needed, but doesn't break -CoW. However, KVM does not mark any newly created stage-2 PTE as Accessed. +CoW. However, on x86, KVM does not mark any newly created stage-2 PTE as +Accessed. In the case of confidential VM types where there is an initial set up of private guest memory before the guest is 'finalized'/measured, this ioctl diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 4f803fd1c99a..6872aaabe16c 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -25,6 +25,7 @@ menuconfig KVM select HAVE_KVM_CPU_RELAX_INTERCEPT select KVM_MMIO select KVM_GENERIC_DIRTYLOG_READ_PROTECT + select KVM_GENERIC_PRE_FAULT_MEMORY select VIRT_XFER_TO_GUEST_WORK select KVM_VFIO select HAVE_KVM_DIRTY_RING_ACQ_REL diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 4f80da0c0d1d..19bac68f737f 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -332,6 +332,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_COUNTER_OFFSET: case KVM_CAP_ARM_WRITABLE_IMP_ID_REGS: case KVM_CAP_ARM_SEA_TO_USER: + case KVM_CAP_PRE_FAULT_MEMORY: r = 1; break; case KVM_CAP_SET_GUEST_DEBUG2: diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 48d7c372a4cd..499b131f794e 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1642,8 +1642,8 @@ static int gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, struct kvm_s2_trans *nested, - struct kvm_memory_slot *memslot, unsigned long hva, - bool fault_is_perm) + struct kvm_memory_slot *memslot, unsigned long *page_size, + unsigned long hva, bool fault_is_perm) { int ret = 0; bool topup_memcache; @@ -1923,6 +1923,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, kvm_release_faultin_page(kvm, page, !!ret, writable); kvm_fault_unlock(kvm); + if (page_size) + *page_size = vma_pagesize; + /* Mark the page dirty only if the fault is handled successfully */ if (writable && !ret) mark_page_dirty_in_slot(kvm, memslot, gfn); @@ -2196,8 +2199,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) ret = gmem_abort(vcpu, fault_ipa, nested, memslot, esr_fsc_is_permission_fault(esr)); else - ret = user_mem_abort(vcpu, fault_ipa, nested, memslot, hva, - esr_fsc_is_permission_fault(esr)); + ret = user_mem_abort(vcpu, fault_ipa, nested, memslot, NULL, + hva, esr_fsc_is_permission_fault(esr)); if (ret == 0) ret = 1; out: @@ -2573,3 +2576,71 @@ void kvm_toggle_cache(struct kvm_vcpu *vcpu, bool was_enabled) trace_kvm_toggle_cache(*vcpu_pc(vcpu), was_enabled, now_enabled); } + +long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, + struct kvm_pre_fault_memory *range) +{ + struct kvm_vcpu_fault_info *fault_info = &vcpu->arch.fault; + struct kvm_s2_trans nested_trans, *nested = NULL; + unsigned long page_size = PAGE_SIZE; + struct kvm_memory_slot *memslot; + phys_addr_t ipa = range->gpa; + phys_addr_t end; + hva_t hva; + gfn_t gfn; + int ret; + + if (vcpu_is_protected(vcpu)) + return -EOPNOTSUPP; + + /* + * We may prefault on a shadow stage 2 page table if we are + * running a nested guest. In this case, we have to resolve the L2 + * IPA to the L1 IPA first, before knowing what kind of memory should + * back the L1 IPA. + * + * If the shadow stage 2 page table walk faults, then we return + * -EFAULT + */ + if (kvm_is_nested_s2_mmu(vcpu->kvm, vcpu->arch.hw_mmu) && + vcpu->arch.hw_mmu->nested_stage2_enabled) { + ret = kvm_walk_nested_s2(vcpu, ipa, &nested_trans); + if (ret) + return -EFAULT; + + ipa = kvm_s2_trans_output(&nested_trans); + nested = &nested_trans; + } + + if (ipa >= kvm_phys_size(vcpu->arch.hw_mmu)) + return -ENOENT; + + /* Generate a synthetic abort for the pre-fault address */ + fault_info->esr_el2 = (ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT) | + ESR_ELx_FSC_FAULT_L(KVM_PGTABLE_LAST_LEVEL); + fault_info->hpfar_el2 = HPFAR_EL2_NS | + FIELD_PREP(HPFAR_EL2_FIPA, ipa >> 12); + + gfn = gpa_to_gfn(ipa); + memslot = gfn_to_memslot(vcpu->kvm, gfn); + if (!memslot) + return -ENOENT; + + if (kvm_slot_has_gmem(memslot)) { + /* gmem currently only supports PAGE_SIZE mappings */ + ret = gmem_abort(vcpu, ipa, nested, memslot, false); + } else { + hva = gfn_to_hva_memslot_prot(memslot, gfn, NULL); + if (kvm_is_error_hva(hva)) + return -EFAULT; + + ret = user_mem_abort(vcpu, ipa, nested, memslot, &page_size, hva, + false); + } + + if (ret < 0) + return ret; + + end = ALIGN_DOWN(range->gpa, page_size) + page_size; + return min(range->size, end - range->gpa); +} -- 2.43.0
