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vfio: ccw: bypass bad idaw address when fetching IDAL ccws

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We currently return the same error code (-EFAULT) to indicate two
different error cases:
1. a bug in vfio-ccw implementation has been found.
2. a buggy channel program has been detected.

This brings difficulty for userland program (specifically Qemu) to
handle.

Let's use -EFAULT to only indicate the first case. For the second
case, we simply hand over the ccws to lower level for further
handling.

Notice:
Once a bad idaw address is detected, the current behavior is to
suppress the ssch. With this fix, the channel program will be
accepted, and part of the channel program (the part ahead of
the bad idaw) could possibly be executed by the device before
I/O conclusion.

Suggested-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Message-Id: <20171011023822.42948-2-bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Dong Jia Shi 2017-10-11 04:38:21 +02:00 committed by Cornelia Huck
parent fe3af62553
commit 688c29533f
1 changed files with 0 additions and 4 deletions
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4
drivers/s390/cio/vfio_ccw_cp.c
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@ -569,10 +569,6 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,
for (i = 0; i < idaw_nr; i++) {
idaw_iova = *(idaws + i);
if (IS_ERR_VALUE(idaw_iova)) {
ret = -EFAULT;
goto out_free_idaws;
}
ret = pfn_array_alloc_pin(pat->pat_pa + i, cp->mdev,
idaw_iova, 1);