KVM: Use pci_store/load_saved_state() around VM device usage

Store the device saved state so that we can reload the device back
to the original state when it's unassigned.  This has the benefit
that the state survives across pci_reset_function() calls via
the PCI sysfs reset interface while the VM is using the device.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

include/linux/kvm_host.h

@@ -513,6 +513,7 @@ struct kvm_assigned_dev_kernel {
 	struct kvm *kvm;
 	spinlock_t intx_lock;
 	char irq_name[32];
+	struct pci_saved_state *pci_saved_state;
 };
 
 struct kvm_irq_mask_notifier {

virt/kvm/assigned-dev.c

@@ -197,8 +197,13 @@ static void kvm_free_assigned_device(struct kvm *kvm,
 {
 	kvm_free_assigned_irq(kvm, assigned_dev);
 
-	__pci_reset_function(assigned_dev->dev);
-	pci_restore_state(assigned_dev->dev);
+	pci_reset_function(assigned_dev->dev);
+	if (pci_load_and_free_saved_state(assigned_dev->dev,
+					  &assigned_dev->pci_saved_state))
+		printk(KERN_INFO "%s: Couldn't reload %s saved state\n",
+		       __func__, dev_name(&assigned_dev->dev->dev));
+	else
+		pci_restore_state(assigned_dev->dev);
 
 	pci_release_regions(assigned_dev->dev);
 	pci_disable_device(assigned_dev->dev);
@@ -516,7 +521,10 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 
 	pci_reset_function(dev);
 	pci_save_state(dev);
-
+	match->pci_saved_state = pci_store_saved_state(dev);
+	if (!match->pci_saved_state)
+		printk(KERN_DEBUG "%s: Couldn't store %s saved state\n",
+		       __func__, dev_name(&dev->dev));
 	match->assigned_dev_id = assigned_dev->assigned_dev_id;
 	match->host_segnr = assigned_dev->segnr;
 	match->host_busnr = assigned_dev->busnr;
@@ -546,7 +554,9 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 	mutex_unlock(&kvm->lock);
 	return r;
 out_list_del:
-	pci_restore_state(dev);
+	if (pci_load_and_free_saved_state(dev, &match->pci_saved_state))
+		printk(KERN_INFO "%s: Couldn't reload %s saved state\n",
+		       __func__, dev_name(&dev->dev));
 	list_del(&match->list);
 	pci_release_regions(dev);
 out_disable: