Re: [PATCH v2 8/8] virtio/s390: make airq summary indicators DMA

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On 28.05.19 16:33, Halil Pasic wrote:
On Mon, 27 May 2019 14:00:18 +0200
Cornelia Huck <cohuck@xxxxxxxxxx> wrote:

On Thu, 23 May 2019 18:22:09 +0200
Michael Mueller <mimu@xxxxxxxxxxxxx> wrote:

From: Halil Pasic <pasic@xxxxxxxxxxxxx>

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 | 22 +++++++++++++++-------
  1 file changed, 15 insertions(+), 7 deletions(-)

(...)

@@ -1501,6 +1508,7 @@ 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);

What happens if this fails?

Bad things could happen!

How about adding

if (!summary_indicators)
	virtio_ccw_use_airq = 0; /* fall back to classic */

?

Since it ain't very likely to happen, we could also just fail
virtio_ccw_init() with -ENOMEM.

That is what I'm currently doing in v3.


Regards,
Halil



  	return ccw_driver_register(&virtio_ccw_driver);
  }
  device_initcall(virtio_ccw_init);



Michael




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