VFIO updates for v3.18-rc1

- Nested IOMMU extension to type1 (Will Deacon)
  - Restore MSIx message before enabling (Gavin Shan)
  - Fix remove path locking (Alex Williamson)
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQIcBAABAgAGBQJUOOETAAoJECObm247sIsihDQP/jADEe9KFu4ymWu7rqi24w1L
 81hGNLXlfx2PPomluN3jENpyueo7vWdP5yZ8q/bi6oF6UbShL8Po01UKHOJzJJwW
 8GW86YcNsmPz/jl8Jcdbkex3dKvT1OzrDjFjCiKTJBHxE9nEdtWlRV8mO1pwd00t
 YFiXF8xFbkpHExMiQNU36rq/fzZCTOu4ZpCK9kDT7Sy+lsKAnGoXuM1IZK+7DGJo
 jcsMF32DVDmji6riy3uHHPc0qprP24QNVy6FfOmLEUvuOEIUOxMAYM9je9mmsHeS
 CeR/NHexr4RgYQE33jL1w8A1saT0rbu7DSKSa7OQebnY2Zte+oncLtqFZR2/Wylh
 jBU5r7P3PdxM6ykqEeC/3ytx7iFX6c7jc0SU4I5m8bFexmUQXqOko28gGIt0OL3n
 R8CmNF/MDs3gqYprhW6MvSJI1diY1+pX7pX0e7k7lDAoZ1QOjPNSGv+YOfF3H1YB
 AggIVxIKXW0T0bQ/hKcQiDKkxQ88vi1hld2LknbiBW9nMNLjNkxl2RZSGunFvWWN
 LzOYkBgR6rrTbhTvsWApsfYguYtGkgAGGJZSR1oev0BJnx4UHOfL1bykJRyUHdUd
 KDSBEni5TY65087IKD93nkyRhassszOa9XHmRDwQLxQeJCKRZi6bQRSzFZVheXIO
 O3XINOo2wNF1bIrfD/vR
 =s2+/
 -----END PGP SIGNATURE-----

Merge tag 'vfio-v3.18-rc1' of git://github.com/awilliam/linux-vfio

Pull VFIO updates from Alex Williamson:
 - Nested IOMMU extension to type1 (Will Deacon)
 - Restore MSIx message before enabling (Gavin Shan)
 - Fix remove path locking (Alex Williamson)

* tag 'vfio-v3.18-rc1' of git://github.com/awilliam/linux-vfio:
  vfio-pci: Fix remove path locking
  drivers/vfio: Export vfio_spapr_iommu_eeh_ioctl() with GPL
  vfio/pci: Restore MSIx message prior to enabling
  PCI: Export MSI message relevant functions
  vfio/iommu_type1: add new VFIO_TYPE1_NESTING_IOMMU IOMMU type
  iommu: introduce domain attribute for nesting IOMMUs

drivers/pci/msi.c

@@ -302,6 +302,7 @@ void get_cached_msi_msg(unsigned int irq, struct msi_msg *msg)
 
 	__get_cached_msi_msg(entry, msg);
 }
+EXPORT_SYMBOL_GPL(get_cached_msi_msg);
 
 void __write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
 {
@@ -346,6 +347,7 @@ void write_msi_msg(unsigned int irq, struct msi_msg *msg)
 
 	__write_msi_msg(entry, msg);
 }
+EXPORT_SYMBOL_GPL(write_msi_msg);
 
 static void free_msi_irqs(struct pci_dev *dev)
 {

drivers/vfio/pci/vfio_pci.c

@@ -876,15 +876,11 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 {
 	struct vfio_pci_device *vdev;
 
-	mutex_lock(&driver_lock);
-
 	vdev = vfio_del_group_dev(&pdev->dev);
 	if (vdev) {
 		iommu_group_put(pdev->dev.iommu_group);
 		kfree(vdev);
 	}
-
-	mutex_unlock(&driver_lock);
 }
 
 static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
@@ -927,108 +923,90 @@ static struct pci_driver vfio_pci_driver = {
 	.err_handler	= &vfio_err_handlers,
 };
 
-/*
- * Test whether a reset is necessary and possible.  We mark devices as
- * needs_reset when they are released, but don't have a function-local reset
- * available.  If any of these exist in the affected devices, we want to do
- * a bus/slot reset.  We also need all of the affected devices to be unused,
- * so we abort if any device has a non-zero refcnt.  driver_lock prevents a
- * device from being opened during the scan or unbound from vfio-pci.
- */
-static int vfio_pci_test_bus_reset(struct pci_dev *pdev, void *data)
-{
-	bool *needs_reset = data;
-	struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);
-	int ret = -EBUSY;
-
-	if (pci_drv == &vfio_pci_driver) {
-		struct vfio_device *device;
-		struct vfio_pci_device *vdev;
-
-		device = vfio_device_get_from_dev(&pdev->dev);
-		if (!device)
-			return ret;
-
-		vdev = vfio_device_data(device);
-		if (vdev) {
-			if (vdev->needs_reset)
-				*needs_reset = true;
-
-			if (!vdev->refcnt)
-				ret = 0;
-		}
-
-		vfio_device_put(device);
-	}
-
-	/*
-	 * TODO: vfio-core considers groups to be viable even if some devices
-	 * are attached to known drivers, like pci-stub or pcieport.  We can't
-	 * freeze devices from being unbound to those drivers like we can
-	 * here though, so it would be racy to test for them.  We also can't
-	 * use device_lock() to prevent changes as that would interfere with
-	 * PCI-core taking device_lock during bus reset.  For now, we require
-	 * devices to be bound to vfio-pci to get a bus/slot reset on release.
-	 */
-
-	return ret;
-}
-
-/* Clear needs_reset on all affected devices after successful bus/slot reset */
-static int vfio_pci_clear_needs_reset(struct pci_dev *pdev, void *data)
+struct vfio_devices {
+	struct vfio_device **devices;
+	int cur_index;
+	int max_index;
+};
+
+static int vfio_pci_get_devs(struct pci_dev *pdev, void *data)
 {
+	struct vfio_devices *devs = data;
 	struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);
 
-	if (pci_drv == &vfio_pci_driver) {
-		struct vfio_device *device;
-		struct vfio_pci_device *vdev;
+	if (pci_drv != &vfio_pci_driver)
+		return -EBUSY;
 
-		device = vfio_device_get_from_dev(&pdev->dev);
-		if (!device)
-			return 0;
+	if (devs->cur_index == devs->max_index)
+		return -ENOSPC;
 
-		vdev = vfio_device_data(device);
-		if (vdev)
-			vdev->needs_reset = false;
-
-		vfio_device_put(device);
-	}
+	devs->devices[devs->cur_index] = vfio_device_get_from_dev(&pdev->dev);
+	if (!devs->devices[devs->cur_index])
+		return -EINVAL;
 
+	devs->cur_index++;
 	return 0;
 }
 
 /*
  * Attempt to do a bus/slot reset if there are devices affected by a reset for
  * this device that are needs_reset and all of the affected devices are unused
- * (!refcnt).  Callers of this function are required to hold driver_lock such
- * that devices can not be unbound from vfio-pci or opened by a user while we
- * test for and perform a bus/slot reset.
+ * (!refcnt).  Callers are required to hold driver_lock when calling this to
+ * prevent device opens and concurrent bus reset attempts.  We prevent device
+ * unbinds by acquiring and holding a reference to the vfio_device.
+ *
+ * NB: vfio-core considers a group to be viable even if some devices are
+ * bound to drivers like pci-stub or pcieport.  Here we require all devices
+ * to be bound to vfio_pci since that's the only way we can be sure they
+ * stay put.
  */
 static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)
 {
+	struct vfio_devices devs = { .cur_index = 0 };
+	int i = 0, ret = -EINVAL;
 	bool needs_reset = false, slot = false;
-	int ret;
+	struct vfio_pci_device *tmp;
 
 	if (!pci_probe_reset_slot(vdev->pdev->slot))
 		slot = true;
 	else if (pci_probe_reset_bus(vdev->pdev->bus))
 		return;
 
+	if (vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs,
+					  &i, slot) || !i)
+		return;
+
+	devs.max_index = i;
+	devs.devices = kcalloc(i, sizeof(struct vfio_device *), GFP_KERNEL);
+	if (!devs.devices)
+		return;
+
 	if (vfio_pci_for_each_slot_or_bus(vdev->pdev,
-					  vfio_pci_test_bus_reset,
-					  &needs_reset, slot) || !needs_reset)
-		return;
+					  vfio_pci_get_devs, &devs, slot))
+		goto put_devs;
 
-	if (slot)
-		ret = pci_try_reset_slot(vdev->pdev->slot);
-	else
-		ret = pci_try_reset_bus(vdev->pdev->bus);
+	for (i = 0; i < devs.cur_index; i++) {
+		tmp = vfio_device_data(devs.devices[i]);
+		if (tmp->needs_reset)
+			needs_reset = true;
+		if (tmp->refcnt)
+			goto put_devs;
+	}
 
-	if (ret)
-		return;
+	if (needs_reset)
+		ret = slot ? pci_try_reset_slot(vdev->pdev->slot) :
+			     pci_try_reset_bus(vdev->pdev->bus);
 
-	vfio_pci_for_each_slot_or_bus(vdev->pdev,
-				      vfio_pci_clear_needs_reset, NULL, slot);
+put_devs:
+	for (i = 0; i < devs.cur_index; i++) {
+		if (!ret) {
+			tmp = vfio_device_data(devs.devices[i]);
+			tmp->needs_reset = false;
+		}
+		vfio_device_put(devs.devices[i]);
+	}
+
+	kfree(devs.devices);
 }
 
 static void __exit vfio_pci_cleanup(void)

drivers/vfio/pci/vfio_pci_intrs.c

@@ -16,6 +16,7 @@
 #include <linux/device.h>
 #include <linux/interrupt.h>
 #include <linux/eventfd.h>
+#include <linux/msi.h>
 #include <linux/pci.h>
 #include <linux/file.h>
 #include <linux/poll.h>
@@ -548,6 +549,20 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
 		return PTR_ERR(trigger);
 	}
 
+	/*
+	 * The MSIx vector table resides in device memory which may be cleared
+	 * via backdoor resets. We don't allow direct access to the vector
+	 * table so even if a userspace driver attempts to save/restore around
+	 * such a reset it would be unsuccessful. To avoid this, restore the
+	 * cached value of the message prior to enabling.
+	 */
+	if (msix) {
+		struct msi_msg msg;
+
+		get_cached_msi_msg(irq, &msg);
+		write_msi_msg(irq, &msg);
+	}
+
 	ret = request_irq(irq, vfio_msihandler, 0,
 			  vdev->ctx[vector].name, trigger);
 	if (ret) {

drivers/vfio/vfio_iommu_type1.c

@@ -57,7 +57,8 @@ struct vfio_iommu {
 	struct list_head	domain_list;
 	struct mutex		lock;
 	struct rb_root		dma_list;
-	bool v2;
+	bool			v2;
+	bool			nesting;
 };
 
 struct vfio_domain {
@@ -705,6 +706,15 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 		goto out_free;
 	}
 
+	if (iommu->nesting) {
+		int attr = 1;
+
+		ret = iommu_domain_set_attr(domain->domain, DOMAIN_ATTR_NESTING,
+					    &attr);
+		if (ret)
+			goto out_domain;
+	}
+
 	ret = iommu_attach_group(domain->domain, iommu_group);
 	if (ret)
 		goto out_domain;
@@ -819,17 +829,26 @@ static void *vfio_iommu_type1_open(unsigned long arg)
 {
 	struct vfio_iommu *iommu;
 
-	if (arg != VFIO_TYPE1_IOMMU && arg != VFIO_TYPE1v2_IOMMU)
-		return ERR_PTR(-EINVAL);
-
 	iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
 	if (!iommu)
 		return ERR_PTR(-ENOMEM);
 
+	switch (arg) {
+	case VFIO_TYPE1_IOMMU:
+		break;
+	case VFIO_TYPE1_NESTING_IOMMU:
+		iommu->nesting = true;
+	case VFIO_TYPE1v2_IOMMU:
+		iommu->v2 = true;
+		break;
+	default:
+		kfree(iommu);
+		return ERR_PTR(-EINVAL);
+	}
+
 	INIT_LIST_HEAD(&iommu->domain_list);
 	iommu->dma_list = RB_ROOT;
 	mutex_init(&iommu->lock);
-	iommu->v2 = (arg == VFIO_TYPE1v2_IOMMU);
 
 	return iommu;
 }
@@ -885,6 +904,7 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 		switch (arg) {
 		case VFIO_TYPE1_IOMMU:
 		case VFIO_TYPE1v2_IOMMU:
+		case VFIO_TYPE1_NESTING_IOMMU:
 			return 1;
 		case VFIO_DMA_CC_IOMMU:
 			if (!iommu)

drivers/vfio/vfio_spapr_eeh.c

@@ -92,7 +92,7 @@ long vfio_spapr_iommu_eeh_ioctl(struct iommu_group *group,
 
 	return ret;
 }
-EXPORT_SYMBOL(vfio_spapr_iommu_eeh_ioctl);
+EXPORT_SYMBOL_GPL(vfio_spapr_iommu_eeh_ioctl);
 
 MODULE_VERSION(DRIVER_VERSION);
 MODULE_LICENSE("GPL v2");

include/linux/iommu.h

@@ -80,6 +80,7 @@ enum iommu_attr {
 	DOMAIN_ATTR_FSL_PAMU_STASH,
 	DOMAIN_ATTR_FSL_PAMU_ENABLE,
 	DOMAIN_ATTR_FSL_PAMUV1,
+	DOMAIN_ATTR_NESTING,	/* two stages of translation */
 	DOMAIN_ATTR_MAX,
 };
 

include/uapi/linux/vfio.h

@@ -33,6 +33,9 @@
 /* Check if EEH is supported */
 #define VFIO_EEH			5
 
+/* Two-stage IOMMU */
+#define VFIO_TYPE1_NESTING_IOMMU	6	/* Implies v2 */
+
 /*
  * The IOCTL interface is designed for extensibility by embedding the
  * structure length (argsz) and flags into structures passed between