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

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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.

  		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);




--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany




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