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lib: test_hmm: use device devt for coherent device range selection

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Commit af69016dab ("lib: test_hmm: implement a device release method")
moved the initial dmirror_allocate_chunk() call before cdev_device_add(). 
That means the struct cdev has not been added yet, so cdev_add() has not
initialized mdevice->cdevice.dev.

The coherent-device range selection uses the device minor to choose
between spm_addr_dev0 and spm_addr_dev1.  Reading
MINOR(mdevice->cdevice.dev) before cdev_add() therefore always sees an
uninitialized dev_t.  As a result, both coherent devices select the same
physical range, and adding the second device fails due to the overlapping
dev_pagemap range.

Use mdevice->device.devt instead.  It is initialized in
dmirror_device_init() before dmirror_allocate_chunk() is called and is the
same dev_t later passed to cdev_device_add().

Link: https://lore.kernel.org/178277581197.172200.16265155329935822153.stgit@skinsburskii
Fixes: af69016dab ("lib: test_hmm: implement a device release method")
Signed-off-by: Stanislav Kinsburskii <skinsburskii@gmail.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: Zenghui Yu (Huawei) <zenghui.yu@linux.dev>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Stanislav Kinsburskii 2026-06-29 16:30:14 -07:00 committed by Andrew Morton
parent ea3034b2b0
commit 4fc0892353
1 changed files with 1 additions and 1 deletions
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2
lib/test_hmm.c
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@ -581,7 +581,7 @@ static int dmirror_allocate_chunk(struct dmirror_device *mdevice,
devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
break;
case HMM_DMIRROR_MEMORY_DEVICE_COHERENT:
devmem->pagemap.range.start = (MINOR(mdevice->cdevice.dev) - 2) ?
devmem->pagemap.range.start = (MINOR(mdevice->device.devt) - 2) ?
spm_addr_dev0 :
spm_addr_dev1;
devmem->pagemap.range.end = devmem->pagemap.range.start +