[dpdk-dev] [PATCH] vfio: fix interrupts race condition

[David Marchand <david.marchand@redhat.com>]

Populating the eventfd in rte_intr_enable in each request to vfio
triggers a reconfiguration of the interrupt handler on the kernel side.
The problem is that rte_intr_enable is often used to re-enable masked
interrupts from drivers interrupt handlers.

This reconfiguration leaves a window during which a device could send
an interrupt and then the kernel logs this (unsolicited from the kernel
point of view) interrupt:
[158764.159833] do_IRQ: 9.34 No irq handler for vector

VFIO api makes it possible to set the fd at setup time.
Make use of this and then we only need to ask for masking/unmasking
legacy interrupts and we have nothing to do for MSI/MSIX.

"rxtx" interrupts are left untouched but are most likely subject to the
same issue.

Fixes: 5c782b3928b8 ("vfio: interrupts")
Cc: stable@dpdk.org

Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1654824
Signed-off-by: David Marchand <david.marchand@redhat.com>
Tested-by: Shahed Shaikh <shshaikh@marvell.com>
---
 drivers/bus/pci/linux/pci_vfio.c          |  78 ++++++------
 lib/librte_eal/linux/eal/eal_interrupts.c | 197 +++++++-----------------------
 2 files changed, 86 insertions(+), 189 deletions(-)

diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c
index 1ceb1c0..ee31239 100644
--- a/drivers/bus/pci/linux/pci_vfio.c
+++ b/drivers/bus/pci/linux/pci_vfio.c
@@ -187,8 +187,11 @@
 static int
 pci_vfio_setup_interrupts(struct rte_pci_device *dev, int vfio_dev_fd)
 {
-	int i, ret, intr_idx;
+	char irq_set_buf[sizeof(struct vfio_irq_set) + sizeof(int)];
+	struct vfio_irq_set *irq_set;
 	enum rte_intr_mode intr_mode;
+	int i, ret, intr_idx;
+	int fd;
 
 	/* default to invalid index */
 	intr_idx = VFIO_PCI_NUM_IRQS;
@@ -220,7 +223,6 @@
 	/* start from MSI-X interrupt type */
 	for (i = VFIO_PCI_MSIX_IRQ_INDEX; i >= 0; i--) {
 		struct vfio_irq_info irq = { .argsz = sizeof(irq) };
-		int fd = -1;
 
 		/* skip interrupt modes we don't want */
 		if (intr_mode != RTE_INTR_MODE_NONE &&
@@ -236,51 +238,51 @@
 			return -1;
 		}
 
+		/* found a usable interrupt mode */
+		if ((irq.flags & VFIO_IRQ_INFO_EVENTFD) != 0)
+			break;
+
 		/* if this vector cannot be used with eventfd, fail if we explicitly
 		 * specified interrupt type, otherwise continue */
-		if ((irq.flags & VFIO_IRQ_INFO_EVENTFD) == 0) {
-			if (intr_mode != RTE_INTR_MODE_NONE) {
-				RTE_LOG(ERR, EAL,
-						"  interrupt vector does not support eventfd!\n");
-				return -1;
-			} else
-				continue;
-		}
-
-		/* set up an eventfd for interrupts */
-		fd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
-		if (fd < 0) {
-			RTE_LOG(ERR, EAL, "  cannot set up eventfd, "
-					"error %i (%s)\n", errno, strerror(errno));
+		if (intr_mode != RTE_INTR_MODE_NONE) {
+			RTE_LOG(ERR, EAL, "  interrupt vector does not support eventfd!\n");
 			return -1;
 		}
+	}
 
-		dev->intr_handle.fd = fd;
-		dev->intr_handle.vfio_dev_fd = vfio_dev_fd;
+	if (i < 0)
+		return -1;
 
-		switch (i) {
-		case VFIO_PCI_MSIX_IRQ_INDEX:
-			intr_mode = RTE_INTR_MODE_MSIX;
-			dev->intr_handle.type = RTE_INTR_HANDLE_VFIO_MSIX;
-			break;
-		case VFIO_PCI_MSI_IRQ_INDEX:
-			intr_mode = RTE_INTR_MODE_MSI;
-			dev->intr_handle.type = RTE_INTR_HANDLE_VFIO_MSI;
-			break;
-		case VFIO_PCI_INTX_IRQ_INDEX:
-			intr_mode = RTE_INTR_MODE_LEGACY;
-			dev->intr_handle.type = RTE_INTR_HANDLE_VFIO_LEGACY;
-			break;
-		default:
-			RTE_LOG(ERR, EAL, "  unknown interrupt type!\n");
-			return -1;
-		}
+	fd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+	if (fd < 0) {
+		RTE_LOG(ERR, EAL, "  cannot set up eventfd, error %i (%s)\n",
+			errno, strerror(errno));
+		return -1;
+	}
 
-		return 0;
+	irq_set = (struct vfio_irq_set *)irq_set_buf;
+	irq_set->argsz = sizeof(irq_set_buf);
+	irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD|VFIO_IRQ_SET_ACTION_TRIGGER;
+	irq_set->index = i;
+	irq_set->start = 0;
+	irq_set->count = 1;
+	memcpy(&irq_set->data, &fd, sizeof(int));
+	if (ioctl(vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set) < 0) {
+		RTE_LOG(ERR, EAL, "  error configuring interrupt\n");
+		close(fd);
+		return -1;
 	}
 
-	/* if we're here, we haven't found a suitable interrupt vector */
-	return -1;
+	dev->intr_handle.fd = fd;
+	dev->intr_handle.vfio_dev_fd = vfio_dev_fd;
+	if (i == VFIO_PCI_MSIX_IRQ_INDEX)
+		dev->intr_handle.type = RTE_INTR_HANDLE_VFIO_MSIX;
+	else if (i == VFIO_PCI_MSI_IRQ_INDEX)
+		dev->intr_handle.type = RTE_INTR_HANDLE_VFIO_MSI;
+	else if (i == VFIO_PCI_INTX_IRQ_INDEX)
+		dev->intr_handle.type = RTE_INTR_HANDLE_VFIO_LEGACY;
+
+	return 0;
 }
 
 #ifdef HAVE_VFIO_DEV_REQ_INTERFACE
diff --git a/lib/librte_eal/linux/eal/eal_interrupts.c b/lib/librte_eal/linux/eal/eal_interrupts.c
index 79ad5e8..27976b3 100644
--- a/lib/librte_eal/linux/eal/eal_interrupts.c
+++ b/lib/librte_eal/linux/eal/eal_interrupts.c
@@ -109,42 +109,19 @@ struct rte_intr_source {
 
 /* enable legacy (INTx) interrupts */
 static int
-vfio_enable_intx(const struct rte_intr_handle *intr_handle) {
-	struct vfio_irq_set *irq_set;
-	char irq_set_buf[IRQ_SET_BUF_LEN];
-	int len, ret;
-	int *fd_ptr;
-
-	len = sizeof(irq_set_buf);
-
-	/* enable INTx */
-	irq_set = (struct vfio_irq_set *) irq_set_buf;
-	irq_set->argsz = len;
-	irq_set->count = 1;
-	irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER;
-	irq_set->index = VFIO_PCI_INTX_IRQ_INDEX;
-	irq_set->start = 0;
-	fd_ptr = (int *) &irq_set->data;
-	*fd_ptr = intr_handle->fd;
-
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
-
-	if (ret) {
-		RTE_LOG(ERR, EAL, "Error enabling INTx interrupts for fd %d\n",
-						intr_handle->fd);
-		return -1;
-	}
+vfio_enable_intx(const struct rte_intr_handle *intr_handle)
+{
+	struct vfio_irq_set irq_set;
+	int ret;
 
-	/* unmask INTx after enabling */
-	memset(irq_set, 0, len);
-	len = sizeof(struct vfio_irq_set);
-	irq_set->argsz = len;
-	irq_set->count = 1;
-	irq_set->flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_UNMASK;
-	irq_set->index = VFIO_PCI_INTX_IRQ_INDEX;
-	irq_set->start = 0;
+	/* unmask INTx */
+	irq_set.argsz = sizeof(irq_set);
+	irq_set.flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_UNMASK;
+	irq_set.index = VFIO_PCI_INTX_IRQ_INDEX;
+	irq_set.start = 0;
+	irq_set.count = 1;
 
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
+	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, &irq_set);
 
 	if (ret) {
 		RTE_LOG(ERR, EAL, "Error unmasking INTx interrupts for fd %d\n",
@@ -156,128 +133,51 @@ struct rte_intr_source {
 
 /* disable legacy (INTx) interrupts */
 static int
-vfio_disable_intx(const struct rte_intr_handle *intr_handle) {
-	struct vfio_irq_set *irq_set;
-	char irq_set_buf[IRQ_SET_BUF_LEN];
-	int len, ret;
-
-	len = sizeof(struct vfio_irq_set);
+vfio_disable_intx(const struct rte_intr_handle *intr_handle)
+{
+	struct vfio_irq_set irq_set;
+	int ret;
 
-	/* mask interrupts before disabling */
-	irq_set = (struct vfio_irq_set *) irq_set_buf;
-	irq_set->argsz = len;
-	irq_set->count = 1;
-	irq_set->flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_MASK;
-	irq_set->index = VFIO_PCI_INTX_IRQ_INDEX;
-	irq_set->start = 0;
+	/* mask interrupts */
+	irq_set.argsz = sizeof(irq_set);
+	irq_set.flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_MASK;
+	irq_set.index = VFIO_PCI_INTX_IRQ_INDEX;
+	irq_set.start = 0;
+	irq_set.count = 1;
 
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
+	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, &irq_set);
 
 	if (ret) {
 		RTE_LOG(ERR, EAL, "Error masking INTx interrupts for fd %d\n",
 						intr_handle->fd);
 		return -1;
 	}
-
-	/* disable INTx*/
-	memset(irq_set, 0, len);
-	irq_set->argsz = len;
-	irq_set->count = 0;
-	irq_set->flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_TRIGGER;
-	irq_set->index = VFIO_PCI_INTX_IRQ_INDEX;
-	irq_set->start = 0;
-
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
-
-	if (ret) {
-		RTE_LOG(ERR, EAL,
-			"Error disabling INTx interrupts for fd %d\n", intr_handle->fd);
-		return -1;
-	}
-	return 0;
-}
-
-/* enable MSI interrupts */
-static int
-vfio_enable_msi(const struct rte_intr_handle *intr_handle) {
-	int len, ret;
-	char irq_set_buf[IRQ_SET_BUF_LEN];
-	struct vfio_irq_set *irq_set;
-	int *fd_ptr;
-
-	len = sizeof(irq_set_buf);
-
-	irq_set = (struct vfio_irq_set *) irq_set_buf;
-	irq_set->argsz = len;
-	irq_set->count = 1;
-	irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER;
-	irq_set->index = VFIO_PCI_MSI_IRQ_INDEX;
-	irq_set->start = 0;
-	fd_ptr = (int *) &irq_set->data;
-	*fd_ptr = intr_handle->fd;
-
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
-
-	if (ret) {
-		RTE_LOG(ERR, EAL, "Error enabling MSI interrupts for fd %d\n",
-						intr_handle->fd);
-		return -1;
-	}
 	return 0;
 }
 
-/* disable MSI interrupts */
-static int
-vfio_disable_msi(const struct rte_intr_handle *intr_handle) {
-	struct vfio_irq_set *irq_set;
-	char irq_set_buf[IRQ_SET_BUF_LEN];
-	int len, ret;
-
-	len = sizeof(struct vfio_irq_set);
-
-	irq_set = (struct vfio_irq_set *) irq_set_buf;
-	irq_set->argsz = len;
-	irq_set->count = 0;
-	irq_set->flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_TRIGGER;
-	irq_set->index = VFIO_PCI_MSI_IRQ_INDEX;
-	irq_set->start = 0;
-
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
-
-	if (ret)
-		RTE_LOG(ERR, EAL,
-			"Error disabling MSI interrupts for fd %d\n", intr_handle->fd);
-
-	return ret;
-}
-
 /* enable MSI-X interrupts */
 static int
-vfio_enable_msix(const struct rte_intr_handle *intr_handle) {
-	int len, ret;
+vfio_enable_msix(const struct rte_intr_handle *intr_handle)
+{
 	char irq_set_buf[MSIX_IRQ_SET_BUF_LEN];
 	struct vfio_irq_set *irq_set;
-	int *fd_ptr;
+	int len, ret;
+
+	if (intr_handle->nb_efd == 0)
+		return 0;
 
 	len = sizeof(irq_set_buf);
 
 	irq_set = (struct vfio_irq_set *) irq_set_buf;
 	irq_set->argsz = len;
-	/* 0 < irq_set->count < RTE_MAX_RXTX_INTR_VEC_ID + 1 */
-	irq_set->count = intr_handle->max_intr ?
-		(intr_handle->max_intr > RTE_MAX_RXTX_INTR_VEC_ID + 1 ?
-		RTE_MAX_RXTX_INTR_VEC_ID + 1 : intr_handle->max_intr) : 1;
 	irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER;
 	irq_set->index = VFIO_PCI_MSIX_IRQ_INDEX;
-	irq_set->start = 0;
-	fd_ptr = (int *) &irq_set->data;
-	/* INTR vector offset 0 reserve for non-efds mapping */
-	fd_ptr[RTE_INTR_VEC_ZERO_OFFSET] = intr_handle->fd;
-	memcpy(&fd_ptr[RTE_INTR_VEC_RXTX_OFFSET], intr_handle->efds,
-		sizeof(*intr_handle->efds) * intr_handle->nb_efd);
+	irq_set->start = RTE_INTR_VEC_RXTX_OFFSET;
+	irq_set->count = intr_handle->nb_efd;
+	memcpy(&irq_set->data, intr_handle->efds,
+	       sizeof(*intr_handle->efds) * intr_handle->nb_efd);
 
 	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
-
 	if (ret) {
 		RTE_LOG(ERR, EAL, "Error enabling MSI-X interrupts for fd %d\n",
 						intr_handle->fd);
@@ -289,22 +189,21 @@ struct rte_intr_source {
 
 /* disable MSI-X interrupts */
 static int
-vfio_disable_msix(const struct rte_intr_handle *intr_handle) {
-	struct vfio_irq_set *irq_set;
-	char irq_set_buf[MSIX_IRQ_SET_BUF_LEN];
-	int len, ret;
-
-	len = sizeof(struct vfio_irq_set);
+vfio_disable_msix(const struct rte_intr_handle *intr_handle)
+{
+	struct vfio_irq_set irq_set;
+	int ret;
 
-	irq_set = (struct vfio_irq_set *) irq_set_buf;
-	irq_set->argsz = len;
-	irq_set->count = 0;
-	irq_set->flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_TRIGGER;
-	irq_set->index = VFIO_PCI_MSIX_IRQ_INDEX;
-	irq_set->start = 0;
+	if (intr_handle->nb_efd == 0)
+		return 0;
 
-	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, irq_set);
+	irq_set.argsz = sizeof(irq_set);
+	irq_set.flags = VFIO_IRQ_SET_DATA_NONE | VFIO_IRQ_SET_ACTION_TRIGGER;
+	irq_set.index = VFIO_PCI_MSIX_IRQ_INDEX;
+	irq_set.start = RTE_INTR_VEC_RXTX_OFFSET;
+	irq_set.count = intr_handle->nb_efd;
 
+	ret = ioctl(intr_handle->vfio_dev_fd, VFIO_DEVICE_SET_IRQS, &irq_set);
 	if (ret)
 		RTE_LOG(ERR, EAL,
 			"Error disabling MSI-X interrupts for fd %d\n", intr_handle->fd);
@@ -665,9 +564,7 @@ struct rte_intr_source {
 			return -1;
 		break;
 	case RTE_INTR_HANDLE_VFIO_MSI:
-		if (vfio_enable_msi(intr_handle))
-			return -1;
-		break;
+		return 0;
 	case RTE_INTR_HANDLE_VFIO_LEGACY:
 		if (vfio_enable_intx(intr_handle))
 			return -1;
@@ -721,9 +618,7 @@ struct rte_intr_source {
 			return -1;
 		break;
 	case RTE_INTR_HANDLE_VFIO_MSI:
-		if (vfio_disable_msi(intr_handle))
-			return -1;
-		break;
+		return 0;
 	case RTE_INTR_HANDLE_VFIO_LEGACY:
 		if (vfio_disable_intx(intr_handle))
 			return -1;
-- 
1.8.3.1