[PATCH v7 7/7] iommu/virtio: Add event queue

Jean-Philippe Brucker
2019-01-15T12:19:59Z

The event queue offers a way for the device to report access faults from
endpoints. It is implemented on virtqueue #1. Whenever the host needs to
signal a fault, it fills one of the buffers offered by the guest and
interrupts it.

Tested-by: Bharat Bhushan <bharat.bhushan@nxp.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
---
drivers/iommu/virtio-iommu.c | 115 +++++++++++++++++++++++++++---
include/uapi/linux/virtio_iommu.h | 19 +++++
2 files changed, 125 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 5e194493a531..4620dd221ffd 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -29,7 +29,8 @@
#define MSI_IOVA_LENGTH 0x100000

#define VIOMMU_REQUEST_VQ 0
-#define VIOMMU_NR_VQS 1
+#define VIOMMU_EVENT_VQ 1
+#define VIOMMU_NR_VQS 2

struct viommu_dev {
struct iommu_device iommu;
@@ -41,6 +42,7 @@ struct viommu_dev {
struct virtqueue *vqs[VIOMMU_NR_VQS];
spinlock_t request_lock;
struct list_head requests;
+ void *evts;

/* Device configuration */
struct iommu_domain_geometry geometry;
@@ -82,6 +84,15 @@ struct viommu_request {
char buf[];
};

+#define VIOMMU_FAULT_RESV_MASK 0xffffff00
+
+struct viommu_event {
+ union {
+ u32 head;
+ struct virtio_iommu_fault fault;
+ };
+};
+
#define to_viommu_domain(domain) \
container_of(domain, struct viommu_domain, domain)

@@ -503,6 +514,68 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
return ret;
}

+static int viommu_fault_handler(struct viommu_dev *viommu,
+ struct virtio_iommu_fault *fault)
+{
+ char *reason_str;
+
+ u8 reason = fault->reason;
+ u32 flags = le32_to_cpu(fault->flags);
+ u32 endpoint = le32_to_cpu(fault->endpoint);
+ u64 address = le64_to_cpu(fault->address);
+
+ switch (reason) {
+ case VIRTIO_IOMMU_FAULT_R_DOMAIN:
+ reason_str = "domain";
+ break;
+ case VIRTIO_IOMMU_FAULT_R_MAPPING:
+ reason_str = "page";
+ break;
+ case VIRTIO_IOMMU_FAULT_R_UNKNOWN:
+ default:
+ reason_str = "unknown";
+ break;
+ }
+
+ /* TODO: find EP by ID and report_iommu_fault */
+ if (flags & VIRTIO_IOMMU_FAULT_F_ADDRESS)
+ dev_err_ratelimited(viommu->dev, "%s fault from EP %u at %#llx [%s%s%s]\n",
+ reason_str, endpoint, address,
+ flags & VIRTIO_IOMMU_FAULT_F_READ ? "R" : "",
+ flags & VIRTIO_IOMMU_FAULT_F_WRITE ? "W" : "",
+ flags & VIRTIO_IOMMU_FAULT_F_EXEC ? "X" : "");
+ else
+ dev_err_ratelimited(viommu->dev, "%s fault from EP %u\n",
+ reason_str, endpoint);
+ return 0;
+}
+
+static void viommu_event_handler(struct virtqueue *vq)
+{
+ int ret;
+ unsigned int len;
+ struct scatterlist sg[1];
+ struct viommu_event *evt;
+ struct viommu_dev *viommu = vq->vdev->priv;
+
+ while ((evt = virtqueue_get_buf(vq, &len)) != NULL) {
+ if (len > sizeof(*evt)) {
+ dev_err(viommu->dev,
+ "invalid event buffer (len %u != %zu)\n",
+ len, sizeof(*evt));
+ } else if (!(evt->head & VIOMMU_FAULT_RESV_MASK)) {
+ viommu_fault_handler(viommu, &evt->fault);
+ }
+
+ sg_init_one(sg, evt, sizeof(*evt));
+ ret = virtqueue_add_inbuf(vq, sg, 1, evt, GFP_ATOMIC);
+ if (ret)
+ dev_err(viommu->dev, "could not add event buffer\n");
+ }
+
+ virtqueue_kick(vq);
+}
+
/* IOMMU API */

static struct iommu_domain *viommu_domain_alloc(unsigned type)
@@ -886,16 +959,35 @@ static struct iommu_ops viommu_ops = {
static int viommu_init_vqs(struct viommu_dev *viommu)
{
struct virtio_device *vdev = dev_to_virtio(viommu->dev);
- const char *name = "request";
- void *ret;
+ const char *names[] = { "request", "event" };
+ vq_callback_t *callbacks[] = {
+ NULL, /* No async requests */
+ viommu_event_handler,
+ };

- ret = virtio_find_single_vq(vdev, NULL, name);
- if (IS_ERR(ret)) {
- dev_err(viommu->dev, "cannot find VQ\n");
- return PTR_ERR(ret);
- }
+ return virtio_find_vqs(vdev, VIOMMU_NR_VQS, viommu->vqs, callbacks,
+ names, NULL);
+}

- viommu->vqs[VIOMMU_REQUEST_VQ] = ret;
+static int viommu_fill_evtq(struct viommu_dev *viommu)
+{
+ int i, ret;
+ struct scatterlist sg[1];
+ struct viommu_event *evts;
+ struct virtqueue *vq = viommu->vqs[VIOMMU_EVENT_VQ];
+ size_t nr_evts = vq->num_free;
+
+ viommu->evts = evts = devm_kmalloc_array(viommu->dev, nr_evts,
+ sizeof(*evts), GFP_KERNEL);
+ if (!evts)
+ return -ENOMEM;
+
+ for (i = 0; i < nr_evts; i++) {
+ sg_init_one(sg, &evts[i], sizeof(*evts));
+ ret = virtqueue_add_inbuf(vq, sg, 1, &evts[i], GFP_KERNEL);
+ if (ret)
+ return ret;
+ }

return 0;
}
@@ -964,6 +1056,11 @@ static int viommu_probe(struct virtio_device *vdev)

virtio_device_ready(vdev);

+ /* Populate the event queue with buffers */
+ ret = viommu_fill_evtq(viommu);
+ if (ret)
+ goto err_free_vqs;
+
ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL, "%s",
virtio_bus_name(vdev));
if (ret)
diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
index ae6145cf5928..ba1b460c9944 100644
--- a/include/uapi/linux/virtio_iommu.h
+++ b/include/uapi/linux/virtio_iommu.h
@@ -139,4 +139,23 @@ struct virtio_iommu_req_probe {
*/
};

+/* Fault types */
+#define VIRTIO_IOMMU_FAULT_R_UNKNOWN 0
+#define VIRTIO_IOMMU_FAULT_R_DOMAIN 1
+#define VIRTIO_IOMMU_FAULT_R_MAPPING 2
+
+#define VIRTIO_IOMMU_FAULT_F_READ (1 << 0)
+#define VIRTIO_IOMMU_FAULT_F_WRITE (1 << 1)
+#define VIRTIO_IOMMU_FAULT_F_EXEC (1 << 2)
+#define VIRTIO_IOMMU_FAULT_F_ADDRESS (1 << 8)
+
+struct virtio_iommu_fault {
+ __u8 reason;
+ __u8 reserved[3];
+ __le32 flags;
+ __le32 endpoint;
+ __u8 reserved2[4];
+ __le64 address;
+};
+
#endif
--
2.19.1