Re: [PATCH] cxl_test: Limit location for fake CFMWS to mappable range

[Itaru Kitayama <itaru.kitayama@linux.dev>]

> On Jun 10, 2025, at 2:25, Dave Jiang <dave.jiang@intel.com> wrote:
> 
> 
> 
>> On 5/27/25 8:34 AM, Jonathan Cameron wrote:
>> Some architectures (e.g. arm64) only support memory hotplug operations on
>> a restricted set of physical addresses. This applies even when we are
>> faking some CXL fixed memory windows for the purposes of cxl_test.
>> That range can be queried with mhp_get_pluggable_range(true). Use the
>> minimum of that the top of that range and iomem_resource.end to establish
>> the 64GiB region used by cxl_test.
>> 
>> From thread #2 which was related to the issue in #1.
>> 
>> Link: https://lore.kernel.org/linux-cxl/20250522145622.00002633@huawei.com/ #2
>> Reported-by: Itaru Kitayama <itaru.kitayama@linux.dev>
>> Closes: https://github.com/pmem/ndctl/issues/278 #1
>> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
>> Tested-by: Itaru Kitayama <itaru.kitayama@fujitsu.com <mailto:itaru.kitayama@fujitsu.com>
>> Tested-by: Marc Herbert <marc.herbert@linux.intel.com>
>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> Applied to cxl/next
> 
> Added the config check from Alison

Can this go into the 6.16 release cycle -rc2 or -rc3?

Itaru.

> 
>> 
>> ---
>> I haven't given this a fixes tag because it never worked on arm64.
>> So it isn't a regression fix, and I'm not sure we want to back port this
>> which a fixes tag might well trigger.  If people want one shout and I'll
>> try and figure out what is appropriate.
>> ---
>> tools/testing/cxl/test/cxl.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>> 
>> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
>> index 8a5815ca870d..6a25cca5636f 100644
>> --- a/tools/testing/cxl/test/cxl.c
>> +++ b/tools/testing/cxl/test/cxl.c
>> @@ -2,6 +2,7 @@
>> // Copyright(c) 2021 Intel Corporation. All rights reserved.
>> 
>> #include <linux/platform_device.h>
>> +#include <linux/memory_hotplug.h>
>> #include <linux/genalloc.h>
>> #include <linux/module.h>
>> #include <linux/mutex.h>
>> @@ -1328,6 +1329,7 @@ static int cxl_mem_init(void)
>> static __init int cxl_test_init(void)
>> {
>>    int rc, i;
>> +    struct range mappable;
>> 
>>    cxl_acpi_test();
>>    cxl_core_test();
>> @@ -1342,8 +1344,11 @@ static __init int cxl_test_init(void)
>>        rc = -ENOMEM;
>>        goto err_gen_pool_create;
>>    }
>> +    mappable = mhp_get_pluggable_range(true);
>> 
>> -    rc = gen_pool_add(cxl_mock_pool, iomem_resource.end + 1 - SZ_64G,
>> +    rc = gen_pool_add(cxl_mock_pool,
>> +              min(iomem_resource.end + 1 - SZ_64G,
>> +                  mappable.end + 1 - SZ_64G),
>>              SZ_64G, NUMA_NO_NODE);
>>    if (rc)
>>        goto err_gen_pool_add;
>