[RFC PATCH 2/3] KVM: x86: use memory_prepare in fetch helper function

[Bandan Das <bsd@redhat.com>]

Insn fetch fastpath function. Not that
arch.walk_mmu->gva_to_gpa can't be used but let's
piggyback on top of interface meant for our purpose

Signed-off-by: Bandan Das <bsd@redhat.com>
---
 arch/x86/kvm/x86.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 17e3d661..cf69e3b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4065,29 +4065,38 @@ static int kvm_read_guest_virt_helper(gva_t addr, void *val, unsigned int bytes,
 				      struct x86_exception *exception)
 {
 	void *data = val;
-	struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
 	int r = X86EMUL_CONTINUE;
 
 	while (bytes) {
-		gpa_t gpa = vcpu->arch.walk_mmu->gva_to_gpa(vcpu, addr, access,
-							    exception);
 		unsigned offset = addr & (PAGE_SIZE-1);
 		unsigned toread = min(bytes, (unsigned)PAGE_SIZE - offset);
 		int ret;
+		unsigned long uaddr;
 
-		if (gpa == UNMAPPED_GVA)
-			return X86EMUL_PROPAGATE_FAULT;
-		ret = kvm_read_guest(vcpu->kvm, gpa, data, toread);
+		ret = ctxt->ops->memory_prepare(ctxt, addr, toread,
+						exception, false,
+						NULL, &uaddr);
+		if (ret != X86EMUL_CONTINUE)
+			return ret;
+
+		if (unlikely(kvm_is_error_hva(uaddr))) {
+			r = X86EMUL_PROPAGATE_FAULT;
+			return r;
+		}
+
+		ret = __copy_from_user(data, (void __user *)uaddr, toread);
 		if (ret < 0) {
 			r = X86EMUL_IO_NEEDED;
-			goto out;
+			return r;
 		}
 
+		ctxt->ops->memory_finish(ctxt, NULL, uaddr);
+
 		bytes -= toread;
 		data += toread;
 		addr += toread;
 	}
-out:
+
 	return r;
 }
 
-- 
1.8.3.1