KVM: Fix page-crossing MMIO

MMIO that are split across a page boundary are currently broken - the
code does not expect to be aborted by the exit to userspace for the
first MMIO fragment.

This patch fixes the problem by generalizing the current code for handling
16-byte MMIOs to handle a number of "fragments", and changes the MMIO
code to create those fragments.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/ia64/include/asm/kvm_host.h

@@ -449,6 +449,8 @@ struct kvm_vcpu_arch {
 	char log_buf[VMM_LOG_LEN];
 	union context host;
 	union context guest;
+
+	char mmio_data[8];
 };
 
 struct kvm_vm_stat {

arch/ia64/kvm/kvm-ia64.c

@@ -232,12 +232,12 @@ static int handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	if ((p->addr & PAGE_MASK) == IOAPIC_DEFAULT_BASE_ADDRESS)
 		goto mmio;
 	vcpu->mmio_needed = 1;
-	vcpu->mmio_phys_addr = kvm_run->mmio.phys_addr = p->addr;
-	vcpu->mmio_size = kvm_run->mmio.len = p->size;
+	vcpu->mmio_fragments[0].gpa = kvm_run->mmio.phys_addr = p->addr;
+	vcpu->mmio_fragments[0].len = kvm_run->mmio.len = p->size;
 	vcpu->mmio_is_write = kvm_run->mmio.is_write = !p->dir;
 
 	if (vcpu->mmio_is_write)
-		memcpy(vcpu->mmio_data, &p->data, p->size);
+		memcpy(vcpu->arch.mmio_data, &p->data, p->size);
 	memcpy(kvm_run->mmio.data, &p->data, p->size);
 	kvm_run->exit_reason = KVM_EXIT_MMIO;
 	return 0;
@@ -719,7 +719,7 @@ static void kvm_set_mmio_data(struct kvm_vcpu *vcpu)
 	struct kvm_mmio_req *p = kvm_get_vcpu_ioreq(vcpu);
 
 	if (!vcpu->mmio_is_write)
-		memcpy(&p->data, vcpu->mmio_data, 8);
+		memcpy(&p->data, vcpu->arch.mmio_data, 8);
 	p->state = STATE_IORESP_READY;
 }
 
@@ -739,7 +739,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	}
 
 	if (vcpu->mmio_needed) {
-		memcpy(vcpu->mmio_data, kvm_run->mmio.data, 8);
+		memcpy(vcpu->arch.mmio_data, kvm_run->mmio.data, 8);
 		kvm_set_mmio_data(vcpu);
 		vcpu->mmio_read_completed = 1;
 		vcpu->mmio_needed = 0;