vdpa/sfc: resolve race between vhost lib and device conf

libvhost calls dev_conf() before prosessing the
VHOST_USER_SET_VRING_CALL message for the last VQ. So
this message is processed after dev_conf() returns.

However, the dev_conf() function spawns a thread to set
rte_vhost_host_notifier_ctrl() before returning control to
libvhost. This parallel thread in turn invokes get_notify_area().
To get the notify_area, the vdpa driver needs to query the HW and
for this query it needs an enabled VQ.

But at the same time libvhost is processing the last
VHOST_USER_SET_VRING_CALL, and to do that it disables the last VQ.

Hence there is a race b/w the libvhost and the vdpa driver.

To resolve this race condition, query the HW and cache notify_area
inside dev_conf() instead of doing it the parallel thread.

Fixes: 630be406dcbf ("vdpa/sfc: get queue notify area info")
Cc: stable@dpdk.org
Signed-off-by: Abhimanyu Saini <absaini@amd.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/drivers/vdpa/sfc/sfc_vdpa_ops.c b/drivers/vdpa/sfc/sfc_vdpa_ops.c
index 63aa52d..b84699d 100644 (file)
--- a/drivers/vdpa/sfc/sfc_vdpa_ops.c
+++ b/drivers/vdpa/sfc/sfc_vdpa_ops.c
@@ -222,6 +222,7 @@ static int
 sfc_vdpa_virtq_start(struct sfc_vdpa_ops_data *ops_data, int vq_num)
 {
        int rc;
+       uint32_t doorbell;
        efx_virtio_vq_t *vq;
        struct sfc_vdpa_vring_info vring;
        efx_virtio_vq_cfg_t vq_cfg;
@@ -270,22 +271,35 @@ sfc_vdpa_virtq_start(struct sfc_vdpa_ops_data *ops_data, int vq_num)
        /* Start virtqueue */
        rc = efx_virtio_qstart(vq, &vq_cfg, &vq_dyncfg);
        if (rc != 0) {
-               /* destroy virtqueue */
                sfc_vdpa_err(ops_data->dev_handle,
                             "virtqueue start failed: %s",
                             rte_strerror(rc));
-               efx_virtio_qdestroy(vq);
                goto fail_virtio_qstart;
        }
 
        sfc_vdpa_info(ops_data->dev_handle,
                      "virtqueue started successfully for vq_num %d", vq_num);
 
+       rc = efx_virtio_get_doorbell_offset(vq, &doorbell);
+       if (rc != 0) {
+               sfc_vdpa_err(ops_data->dev_handle,
+                            "failed to get doorbell offset: %s",
+                            rte_strerror(rc));
+               goto fail_doorbell;
+       }
+
+       /*
+        * Cache the bar_offset here for each VQ here, it will come
+        * in handy when sfc_vdpa_get_notify_area() is invoked.
+        */
+       ops_data->vq_cxt[vq_num].doorbell = (void *)(uintptr_t)doorbell;
        ops_data->vq_cxt[vq_num].enable = B_TRUE;
 
        return rc;
 
+fail_doorbell:
 fail_virtio_qstart:
+       efx_virtio_qdestroy(vq);
 fail_vring_info:
        return rc;
 }
@@ -792,8 +806,6 @@ sfc_vdpa_get_notify_area(int vid, int qid, uint64_t *offset, uint64_t *size)
        int ret;
        efx_nic_t *nic;
        int vfio_dev_fd;
-       efx_rc_t rc;
-       unsigned int bar_offset;
        volatile void *doorbell;
        struct rte_pci_device *pci_dev;
        struct rte_vdpa_device *vdpa_dev;
@@ -824,19 +836,6 @@ sfc_vdpa_get_notify_area(int vid, int qid, uint64_t *offset, uint64_t *size)
                return -1;
        }
 
-       if (ops_data->vq_cxt[qid].enable != B_TRUE) {
-               sfc_vdpa_err(dev, "vq is not enabled");
-               return -1;
-       }
-
-       rc = efx_virtio_get_doorbell_offset(ops_data->vq_cxt[qid].vq,
-                                           &bar_offset);
-       if (rc != 0) {
-               sfc_vdpa_err(dev, "failed to get doorbell offset: %s",
-                            rte_strerror(rc));
-               return rc;
-       }
-
        reg.index = sfc_vdpa_adapter_by_dev_handle(dev)->mem_bar.esb_rid;
        ret = ioctl(vfio_dev_fd, VFIO_DEVICE_GET_REGION_INFO, &reg);
        if (ret != 0) {
@@ -845,7 +844,8 @@ sfc_vdpa_get_notify_area(int vid, int qid, uint64_t *offset, uint64_t *size)
                return ret;
        }
 
-       *offset = reg.offset + bar_offset;
+       /* Use bar_offset that was cached during sfc_vdpa_virtq_start() */
+       *offset = reg.offset + (uint64_t)ops_data->vq_cxt[qid].doorbell;
 
        len = (1U << encp->enc_vi_window_shift) / 2;
        if (len >= sysconf(_SC_PAGESIZE)) {

diff --git a/drivers/vdpa/sfc/sfc_vdpa_ops.h b/drivers/vdpa/sfc/sfc_vdpa_ops.h
index 6d790fd..9dbd5b8 100644 (file)
--- a/drivers/vdpa/sfc/sfc_vdpa_ops.h
+++ b/drivers/vdpa/sfc/sfc_vdpa_ops.h
@@ -35,6 +35,7 @@ struct sfc_vdpa_vring_info {
 };
 
 typedef struct sfc_vdpa_vq_context_s {
+       volatile void                   *doorbell;
        uint8_t                         enable;
        uint32_t                        pidx;
        uint32_t                        cidx;