Re: [PATCH 10/10] virtio/s390: make airq summary indicators DMA

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On 08.05.19 17:11, Pierre Morel wrote:
On 26/04/2019 20:32, Halil Pasic wrote:
Hypervisor needs to interact with the summary indicators, so these
need to be DMA memory as well (at least for protected virtualization
guests).

Signed-off-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
---
  drivers/s390/virtio/virtio_ccw.c | 24 +++++++++++++++++-------
  1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index 613b18001a0c..6058b07fea08 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -140,11 +140,17 @@ static int virtio_ccw_use_airq = 1;
  struct airq_info {
      rwlock_t lock;
-    u8 summary_indicator;
+    u8 summary_indicator_idx;
      struct airq_struct airq;
      struct airq_iv *aiv;
  };
  static struct airq_info *airq_areas[MAX_AIRQ_AREAS];
+static u8 *summary_indicators;
+
+static inline u8 *get_summary_indicator(struct airq_info *info)
+{
+    return summary_indicators + info->summary_indicator_idx;
+}
  #define CCW_CMD_SET_VQ 0x13
  #define CCW_CMD_VDEV_RESET 0x33
@@ -225,7 +231,7 @@ static void virtio_airq_handler(struct airq_struct *airq)
              break;
          vring_interrupt(0, (void *)airq_iv_get_ptr(info->aiv, ai));
      }
-    info->summary_indicator = 0;
+    *(get_summary_indicator(info)) = 0;
      smp_wmb();
      /* Walk through indicators field, summary indicator not active. */
      for (ai = 0;;) {
@@ -237,7 +243,8 @@ static void virtio_airq_handler(struct airq_struct *airq)
      read_unlock(&info->lock);
  }
-static struct airq_info *new_airq_info(void)
+/* call with airq_areas_lock held */
+static struct airq_info *new_airq_info(int index)
  {
      struct airq_info *info;
      int rc;
@@ -252,7 +259,8 @@ static struct airq_info *new_airq_info(void)
          return NULL;
      }
      info->airq.handler = virtio_airq_handler;
-    info->airq.lsi_ptr = &info->summary_indicator;
+    info->summary_indicator_idx = index;
+    info->airq.lsi_ptr = get_summary_indicator(info);
      info->airq.lsi_mask = 0xff;
      info->airq.isc = VIRTIO_AIRQ_ISC;
      rc = register_adapter_interrupt(&info->airq);
@@ -273,8 +281,9 @@ static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs,
      unsigned long bit, flags;
      for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) {
+        /* TODO: this seems to be racy */

yes, my opinions too, was already racy, in my opinion, we need another patch in another series to fix this.

However, not sure about the comment.

I will drop this comment for v2 of this patch series.
We shall fix the race with a separate patch.

Michael


          if (!airq_areas[i])
-            airq_areas[i] = new_airq_info();
+            airq_areas[i] = new_airq_info(i);
          info = airq_areas[i];
          if (!info)
              return 0;
@@ -359,7 +368,7 @@ static void virtio_ccw_drop_indicator(struct virtio_ccw_device *vcdev,
          if (!thinint_area)
              return;
          thinint_area->summary_indicator =
-            (unsigned long) &airq_info->summary_indicator;
+            (unsigned long) get_summary_indicator(airq_info);
          thinint_area->isc = VIRTIO_AIRQ_ISC;
          ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
          ccw->count = sizeof(*thinint_area);
@@ -624,7 +633,7 @@ static int virtio_ccw_register_adapter_ind(struct virtio_ccw_device *vcdev,
      }
      info = vcdev->airq_info;
      thinint_area->summary_indicator =
-        (unsigned long) &info->summary_indicator;
+        (unsigned long) get_summary_indicator(info);
      thinint_area->isc = VIRTIO_AIRQ_ISC;
      ccw->cmd_code = CCW_CMD_SET_IND_ADAPTER;
      ccw->flags = CCW_FLAG_SLI;
@@ -1500,6 +1509,7 @@ static int __init virtio_ccw_init(void)
  {
      /* parse no_auto string before we do anything further */
      no_auto_parse();
+    summary_indicators = cio_dma_zalloc(MAX_AIRQ_AREAS);
      return ccw_driver_register(&virtio_ccw_driver);
  }
  device_initcall(virtio_ccw_init);





--
Mit freundlichen Grüßen / Kind regards
Michael Müller

IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Matthias Hartmann
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294

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