linux-kernel - Re: [RFC PATCH v4 2/9] tools headers: Add a macro to get HUGETLB page sizes for mmap

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Date:   Mon, 15 Mar 2021 10:06:33 +0800
From:   "wangyanan (Y)" <wangyanan55@...wei.com>
To:     Andrew Jones <drjones@...hat.com>
CC:     <kvm@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Ben Gardon" <bgardon@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>,
        Peter Xu <peterx@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...hat.com>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        <wanghaibin.wang@...wei.com>, <yezengruan@...wei.com>,
        <yuzenghui@...wei.com>
Subject: Re: [RFC PATCH v4 2/9] tools headers: Add a macro to get HUGETLB page
 sizes for mmap


On 2021/3/12 19:14, Andrew Jones wrote:
> On Tue, Mar 02, 2021 at 08:57:44PM +0800, Yanan Wang wrote:
>> We know that if a system supports multiple hugetlb page sizes,
>> the desired hugetlb page size can be specified in bits [26:31]
>> of the flag arguments. The value in these 6 bits will be the
>> shift of each hugetlb page size.
>>
>> So add a macro to get the page size shift and then calculate the
>> corresponding hugetlb page size, using flag x.
>>
>> Cc: Ben Gardon <bgardon@...gle.com>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> Cc: Adrian Hunter <adrian.hunter@...el.com>
>> Cc: Jiri Olsa <jolsa@...hat.com>
>> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
>> Cc: Arnd Bergmann <arnd@...db.de>
>> Cc: Michael Kerrisk <mtk.manpages@...il.com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Suggested-by: Ben Gardon <bgardon@...gle.com>
>> Signed-off-by: Yanan Wang <wangyanan55@...wei.com>
>> Reviewed-by: Ben Gardon <bgardon@...gle.com>
>> ---
>>   include/uapi/linux/mman.h       | 2 ++
>>   tools/include/uapi/linux/mman.h | 2 ++
>>   2 files changed, 4 insertions(+)
>>
>> diff --git a/include/uapi/linux/mman.h b/include/uapi/linux/mman.h
>> index f55bc680b5b0..8bd41128a0ee 100644
>> --- a/include/uapi/linux/mman.h
>> +++ b/include/uapi/linux/mman.h
>> @@ -41,4 +41,6 @@
>>   #define MAP_HUGE_2GB	HUGETLB_FLAG_ENCODE_2GB
>>   #define MAP_HUGE_16GB	HUGETLB_FLAG_ENCODE_16GB
>>   
>> +#define MAP_HUGE_PAGE_SIZE(x) (1 << ((x >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK))
> Needs to be '1ULL' to avoid shift overflow when given MAP_HUGE_16GB.
Thanks, drew. Will fix it.
> Thanks,
> drew
>
>> +
>>   #endif /* _UAPI_LINUX_MMAN_H */
>> diff --git a/tools/include/uapi/linux/mman.h b/tools/include/uapi/linux/mman.h
>> index f55bc680b5b0..8bd41128a0ee 100644
>> --- a/tools/include/uapi/linux/mman.h
>> +++ b/tools/include/uapi/linux/mman.h
>> @@ -41,4 +41,6 @@
>>   #define MAP_HUGE_2GB	HUGETLB_FLAG_ENCODE_2GB
>>   #define MAP_HUGE_16GB	HUGETLB_FLAG_ENCODE_16GB
>>   
>> +#define MAP_HUGE_PAGE_SIZE(x) (1 << ((x >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK))
>> +
>>   #endif /* _UAPI_LINUX_MMAN_H */
>> -- 
>> 2.23.0
>>
> .