Re: [PATCH v8 0/3] mm/hmm/test: add self tests for HMM

From: Ralph Campbell <rcampbell@nvidia.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: Jason Gunthorpe <jgg@mellanox.com>,
	Jerome Glisse <jglisse@redhat.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Christoph Hellwig <hch@lst.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	Shuah Khan <shuah@kernel.org>, <linux-rdma@vger.kernel.org>,
	<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
	<linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH v8 0/3] mm/hmm/test: add self tests for HMM
Date: Wed, 15 Apr 2020 12:39:45 -0700	[thread overview]
Message-ID: <1b94e41d-2335-0cb4-9605-cf9f404900c9@nvidia.com> (raw)
In-Reply-To: <20200415192952.GA1309273@unreal>

On 4/15/20 12:29 PM, Leon Romanovsky wrote:
> On Wed, Apr 15, 2020 at 10:28:23AM -0700, Ralph Campbell wrote:
>>
>> On 4/15/20 7:41 AM, Jason Gunthorpe wrote:
>>> On Fri, Mar 20, 2020 at 05:31:05PM -0700, Ralph Campbell wrote:
>>>> This series adds basic self tests for HMM and are intended for Jason
>>>> Gunthorpe's rdma tree which has a number of HMM patches applied.
>>>
>>> Here are some hunks I noticed while testing this:
>>>
>>> --- a/lib/Kconfig.debug
>>> +++ b/lib/Kconfig.debug
>>> @@ -2201,7 +2201,8 @@ config TEST_MEMINIT
>>>    config TEST_HMM
>>>    	tristate "Test HMM (Heterogeneous Memory Management)"
>>> -	depends on DEVICE_PRIVATE
>>> +	depends on TRANSPARENT_HUGEPAGE
>>> +	select DEVICE_PRIVATE
>>>    	select HMM_MIRROR
>>>    	select MMU_NOTIFIER
>>>    	help
>>>
>>> It fails testing if TRANSPARENT_HUGEPAGE is not on
>>>
>>> @@ -1097,6 +1071,7 @@ static int dmirror_device_init(struct dmirror_device *mdevice, int id)
>>>    	spin_lock_init(&mdevice->lock);
>>>    	cdev_init(&mdevice->cdevice, &dmirror_fops);
>>> +	mdevice->cdevice.owner = THIS_MODULE;
>>>    	ret = cdev_add(&mdevice->cdevice, dev, 1);
>>>    	if (ret)
>>>    		return ret;
>>>
>>> The use of cdev without a struct device is super weird, but it still
>>> needs this
>>>
>>> diff --git a/tools/testing/selftests/vm/test_hmm.sh b/tools/testing/selftests/vm/test_hmm.sh
>>> index 461e4a99a362cf..0647b525a62564 100755
>>> --- a/tools/testing/selftests/vm/test_hmm.sh
>>> +++ b/tools/testing/selftests/vm/test_hmm.sh
>>> @@ -59,7 +59,7 @@ run_smoke()
>>>    	echo "Running smoke test. Note, this test provides basic coverage."
>>>    	load_driver
>>> -	./hmm-tests
>>> +	$(dirname "${BASH_SOURCE[0]}")/hmm-tests
>>>    	unload_driver
>>>    }
>>>
>>> Make it runnably reliably
>>>
>>> Jason
>>
>> Thanks for the fixes. I'll apply these and send a v9.
>> I will also add missing calls to release_mem_region() to free the reserved device private
>> addresses.
> 
> If you decide to ignore my request to avoid addition of special header
> file to UAPI, at least don't copy and install that file without some
> special CONFIG option (TEST_HMM ???) requested by the users. It also
> will be good to get Acked-by on this change from HMM people.
> 
> However, I still think that include/uapi/linux/test_hmm.h opens
> pandora box of having UAPI files without real promise to keep it
> backward compatible.
> 
> Thanks

I think that is a valid point. I would expect the test<->driver UAPI to track the kernel
version since the sources are "released" together. I suppose a version number could be
included in the request structure to handle mismatch driver and test program but that
may be overkill.
Are you suggesting that include/linux/test_hmm.h is a better location?