linux-kernel - Re: [PATCH v2 2/7] selftests/mm: Add support to test 4PB VA on PPC64

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Message-ID: <8e7dbebe-59c5-42cc-bc44-570842b8e82c@linux.ibm.com>
Date: Thu, 3 Jul 2025 20:20:15 +0530
From: Donet Tom <donettom@...ux.ibm.com>
To: Zi Yan <ziy@...dia.com>, Aboorva Devarajan <aboorvad@...ux.ibm.com>
Cc: akpm@...ux-foundation.org, Liam.Howlett@...cle.com,
        lorenzo.stoakes@...cle.com, shuah@...nel.org, pfalcato@...e.de,
        david@...hat.com, baolin.wang@...ux.alibaba.com, npache@...hat.com,
        ryan.roberts@....com, dev.jain@....com, baohua@...nel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, ritesh.list@...il.com
Subject: Re: [PATCH v2 2/7] selftests/mm: Add support to test 4PB VA on PPC64


On 7/3/25 8:11 PM, Zi Yan wrote:
> On 3 Jul 2025, at 2:06, Aboorva Devarajan wrote:
>
>> From: Donet Tom <donettom@...ux.ibm.com>
>>
>> PowerPC64 supports a 4PB virtual address space, but this test was
>> previously limited to 512TB. This patch extends the coverage up to
>> the full 4PB VA range on PowerPC64.
>>
>> Memory from 0 to 128TB is allocated without an address hint, while
>> allocations from 128TB to 4PB use a hint address.
>>
>> Signed-off-by: Donet Tom <donettom@...ux.ibm.com>
>> Signed-off-by: Aboorva Devarajan <aboorvad@...ux.ibm.com>
>> ---
>>   tools/testing/selftests/mm/virtual_address_range.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/tools/testing/selftests/mm/virtual_address_range.c b/tools/testing/selftests/mm/virtual_address_range.c
>> index e24c36a39f22..619acf0b9239 100644
>> --- a/tools/testing/selftests/mm/virtual_address_range.c
>> +++ b/tools/testing/selftests/mm/virtual_address_range.c
>> @@ -50,6 +50,7 @@
>>   #define NR_CHUNKS_256TB   (NR_CHUNKS_128TB * 2UL)
>>   #define NR_CHUNKS_384TB   (NR_CHUNKS_128TB * 3UL)
>>   #define NR_CHUNKS_3840TB  (NR_CHUNKS_128TB * 30UL)
>> +#define NR_CHUNKS_3968TB  (NR_CHUNKS_128TB * 31UL)
>>
>>   #define ADDR_MARK_128TB  (1UL << 47) /* First address beyond 128TB */
>>   #define ADDR_MARK_256TB  (1UL << 48) /* First address beyond 256TB */
>> @@ -59,6 +60,11 @@
>>   #define HIGH_ADDR_SHIFT 49
>>   #define NR_CHUNKS_LOW   NR_CHUNKS_256TB
>>   #define NR_CHUNKS_HIGH  NR_CHUNKS_3840TB
>> +#elif defined(__PPC64__)
>> +#define HIGH_ADDR_MARK  ADDR_MARK_128TB
>> +#define HIGH_ADDR_SHIFT 48
>> +#define NR_CHUNKS_LOW   NR_CHUNKS_128TB
>> +#define NR_CHUNKS_HIGH  NR_CHUNKS_3968TB
>>   #else
>>   #define HIGH_ADDR_MARK  ADDR_MARK_128TB
>>   #define HIGH_ADDR_SHIFT 48
> Could you also update the comment above this code to say PowerPC64 also
> supports 4PB virtual address space?


Sure. I will add


>
>  From the comment, arm64 supports 4PB but its NR_CHUNKS_HIGH is only 3840TB,
> whereas PowerPC64 here can get to 3968TB. I do not know why arm64’s
> 4PB is smaller. ;)
>
> Otherwise, the patch looks good to me.
>
> Reviewed-by: Zi Yan <ziy@...dia.com>
>
> Best Regards,
> Yan, Zi