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pc-bios/s390-ccw: Build a reasonable max_sectors limit

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Now that we've read all the possible limits that have been defined for
a virtio-scsi controller and the disk we're booting from, it's possible
that we are STILL going to exceed the limits of the host device.
For example, a "-device scsi-generic" device does not support the
Block Limits VPD page.

So, let's fallback to something that seems to work for most boot
configurations if larger values were specified (including if nothing
was explicitly specified, and we took default values).

Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170510155359.32727-8-farman@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This commit is contained in:
Eric Farman 2017-05-10 17:53:58 +02:00 • committed by Cornelia Huck
parent fe921fc8b7
commit de4e3ae408
2 changed files with 11 additions and 0 deletions
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9
pc-bios/s390-ccw/virtio-scsi.c
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@ -399,6 +399,15 @@ void virtio_scsi_setup(VDev *vdev)
vdev->max_transfer = evpd_bl->max_transfer;
}
/*
* The host sg driver will often be unhappy with particularly large
* I/Os that exceed the block iovec limits. Let's enforce something
* reasonable, despite what the device configuration tells us.
*/
vdev->max_transfer = MIN_NON_ZERO(VIRTIO_SCSI_MAX_SECTORS,
vdev->max_transfer);
if (!scsi_read_capacity(vdev, data, data_size)) {
virtio_scsi_verify_response(&resp, "virtio-scsi:setup:read_capacity");
}