[RFC PATCH 5/8] KVM: x86/mmu: Introduce kvm_mmu_map_page() for prepopulating guest memory

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Introduce a helper function to call kvm fault handler.  This allows
a new ioctl to invoke kvm fault handler to populate without seeing
RET_PF_* enums or other KVM MMU internal definitions.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
 arch/x86/kvm/mmu.h     |  3 +++
 arch/x86/kvm/mmu/mmu.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 60f21bb4c27b..48870c5e08ec 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -183,6 +183,9 @@ static inline void kvm_mmu_refresh_passthrough_bits(struct kvm_vcpu *vcpu,
 	__kvm_mmu_refresh_passthrough_bits(vcpu, mmu);
 }
 
+int kvm_mmu_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
+		     u8 max_level, u8 *goal_level);
+
 /*
  * Check if a given access (described through the I/D, W/R and U/S bits of a
  * page fault error code pfec) causes a permission fault with the given PTE
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e4cc7f764980..7d5e80d17977 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4659,6 +4659,36 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	return direct_page_fault(vcpu, fault);
 }
 
+int kvm_mmu_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
+		     u8 max_level, u8 *goal_level)
+{
+	struct kvm_page_fault fault = KVM_PAGE_FAULT_INIT(vcpu, gpa, error_code,
+							  false, max_level);
+	int r;
+
+	r = __kvm_mmu_do_page_fault(vcpu, &fault);
+
+	if (is_error_noslot_pfn(fault.pfn) || vcpu->kvm->vm_bugged)
+		return -EFAULT;
+
+	switch (r) {
+	case RET_PF_RETRY:
+		return -EAGAIN;
+
+	case RET_PF_FIXED:
+	case RET_PF_SPURIOUS:
+		*goal_level = fault.goal_level;
+		return 0;
+
+	case RET_PF_CONTINUE:
+	case RET_PF_EMULATE:
+	case RET_PF_INVALID:
+	default:
+		return -EIO;
+	}
+}
+EXPORT_SYMBOL_GPL(kvm_mmu_map_page);
+
 static void nonpaging_init_context(struct kvm_mmu *context)
 {
 	context->page_fault = nonpaging_page_fault;
-- 
2.25.1