Re: [PATCH v2 2/2] mm/hmm: add a test for cross device private faults

[Alistair Popple <apopple@nvidia.com>]

Reviewed-by: Alistair Popple <apopple@nvidia.com>

Ralph Campbell <rcampbell@nvidia.com> writes:

> Add a simple test case for when hmm_range_fault() is called with the
> HMM_PFN_REQ_FAULT flag and a device private PTE is found for a device
> other than the hmm_range::dev_private_owner. This should cause the
> page to be faulted back to system memory from the other device and the
> PFN returned in the output array.
>
> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
> ---
>  tools/testing/selftests/vm/hmm-tests.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
> index 203323967b50..a5ce7cc2e7aa 100644
> --- a/tools/testing/selftests/vm/hmm-tests.c
> +++ b/tools/testing/selftests/vm/hmm-tests.c
> @@ -1520,9 +1520,19 @@ TEST_F(hmm2, double_map)
>  	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
>  		ASSERT_EQ(ptr[i], i);
>
> -	/* Punch a hole after the first page address. */
> -	ret = munmap(buffer->ptr + self->page_size, self->page_size);
> +	/* Migrate pages to device 1 and try to read from device 0. */
> +	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, npages);
> +	ASSERT_EQ(ret, 0);
> +	ASSERT_EQ(buffer->cpages, npages);
> +
> +	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_READ, buffer, npages);
>  	ASSERT_EQ(ret, 0);
> +	ASSERT_EQ(buffer->cpages, npages);
> +	ASSERT_EQ(buffer->faults, 1);
> +
> +	/* Check what device 0 read. */
> +	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
> +		ASSERT_EQ(ptr[i], i);
>
>  	hmm_buffer_free(buffer);
>  }