[PATCH v4 11/16] KVM: arm64: Implement KVM_CAP_NOWAIT_ON_FAULT

[Anish Moorthy <amoorthy@google.com>]

Return -EFAULT from user_mem_abort when the memslot flag is enabled and
fast GUP fails to find a present mapping for the page.

Signed-off-by: Anish Moorthy <amoorthy@google.com>
---
 Documentation/virt/kvm/api.rst |  2 +-
 arch/arm64/kvm/arm.c           |  1 +
 arch/arm64/kvm/mmu.c           | 16 +++++++++++++++-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index aa7b4024fd41..8a1205f7c271 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7783,7 +7783,7 @@ bugs and reported to the maintainers so that annotations can be added.
 7.35 KVM_CAP_NOWAIT_ON_FAULT
 ----------------------------
 
-:Architectures: x86
+:Architectures: x86, arm64
 :Returns: -EINVAL.
 
 The presence of this capability indicates that userspace may pass the
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index b34cf0cedffa..46a09c4db901 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -235,6 +235,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_IRQFD_RESAMPLE:
 	case KVM_CAP_COUNTER_OFFSET:
 	case KVM_CAP_MEMORY_FAULT_INFO:
+	case KVM_CAP_NOWAIT_ON_FAULT:
 		r = 1;
 		break;
 	case KVM_CAP_SET_GUEST_DEBUG2:
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 3b9d4d24c361..5451b712b0ac 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1232,6 +1232,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	long vma_pagesize, fault_granule;
 	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
 	struct kvm_pgtable *pgt;
+	bool exit_on_memory_fault = kvm_slot_nowait_on_fault(memslot);
+	uint64_t memory_fault_flags;
 
 	fault_granule = 1UL << ARM64_HW_PGTABLE_LEVEL_SHIFT(fault_level);
 	write_fault = kvm_is_write_fault(vcpu);
@@ -1325,8 +1327,20 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	mmu_seq = vcpu->kvm->mmu_invalidate_seq;
 	mmap_read_unlock(current->mm);
 
-	pfn = __gfn_to_pfn_memslot(memslot, gfn, false, false, NULL,
+	pfn = __gfn_to_pfn_memslot(memslot, gfn, exit_on_memory_fault, false, NULL,
 				   write_fault, &writable, NULL);
+
+	if (exit_on_memory_fault && pfn == KVM_PFN_ERR_FAULT) {
+		memory_fault_flags = 0;
+		if (write_fault)
+			memory_fault_flags |= KVM_MEMORY_FAULT_FLAG_EXEC;
+		if (exec_fault)
+			memory_fault_flags |= KVM_MEMORY_FAULT_FLAG_EXEC;
+		kvm_populate_efault_info(vcpu,
+					 round_down(gfn * PAGE_SIZE, vma_pagesize), vma_pagesize,
+					 memory_fault_flags);
+		return -EFAULT;
+	}
 	if (pfn == KVM_PFN_ERR_HWPOISON) {
 		kvm_send_hwpoison_signal(hva, vma_shift);
 		return 0;
-- 
2.41.0.rc0.172.g3f132b7071-goog