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Subject: Re: [PATCH 1/4] hugetlbfs: add arch_hugetlb_valid_size
To:     Mike Kravetz <mike.kravetz@oracle.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
        linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
        linux-doc@vger.kernel.org
Cc:     Albert Ou <aou@eecs.berkeley.edu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Paul Mackerras <paulus@samba.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Longpeng <longpeng2@huawei.com>, Will Deacon <will@kernel.org>,
        "David S . Miller" <davem@davemloft.net>
References: <20200318220634.32100-1-mike.kravetz@oracle.com>
 <20200318220634.32100-2-mike.kravetz@oracle.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <c3071359-c5d3-4247-7f16-6f61b2fa0756@c-s.fr>
Date:   Thu, 19 Mar 2020 08:00:59 +0100
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Le 18/03/2020 à 23:06, Mike Kravetz a écrit :
> The architecture independent routine hugetlb_default_setup sets up
> the default huge pages size.  It has no way to verify if the passed
> value is valid, so it accepts it and attempts to validate at a later
> time.  This requires undocumented cooperation between the arch specific
> and arch independent code.
> 
> For architectures that support more than one huge page size, provide
> a routine arch_hugetlb_valid_size to validate a huge page size.
> hugetlb_default_setup can use this to validate passed values.
> 
> arch_hugetlb_valid_size will also be used in a subsequent patch to
> move processing of the "hugepagesz=" in arch specific code to a common
> routine in arch independent code.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---
>   arch/arm64/include/asm/hugetlb.h   |  2 ++
>   arch/arm64/mm/hugetlbpage.c        | 19 ++++++++++++++-----
>   arch/powerpc/include/asm/hugetlb.h |  3 +++
>   arch/powerpc/mm/hugetlbpage.c      | 20 +++++++++++++-------
>   arch/riscv/include/asm/hugetlb.h   |  3 +++
>   arch/riscv/mm/hugetlbpage.c        | 28 ++++++++++++++++++----------
>   arch/s390/include/asm/hugetlb.h    |  3 +++
>   arch/s390/mm/hugetlbpage.c         | 18 +++++++++++++-----
>   arch/sparc/include/asm/hugetlb.h   |  3 +++
>   arch/sparc/mm/init_64.c            | 23 ++++++++++++++++-------
>   arch/x86/include/asm/hugetlb.h     |  3 +++
>   arch/x86/mm/hugetlbpage.c          | 21 +++++++++++++++------
>   include/linux/hugetlb.h            |  7 +++++++
>   mm/hugetlb.c                       | 16 +++++++++++++---
>   14 files changed, 126 insertions(+), 43 deletions(-)
> 

[snip]

> diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
> index bd6504c28c2f..3b5939016955 100644
> --- a/arch/powerpc/include/asm/hugetlb.h
> +++ b/arch/powerpc/include/asm/hugetlb.h
> @@ -64,6 +64,9 @@ static inline void arch_clear_hugepage_flags(struct page *page)
>   {
>   }
>   
> +#define arch_hugetlb_valid_size arch_hugetlb_valid_size
> +extern bool __init arch_hugetlb_valid_size(unsigned long long size);

Don't add 'extern' keyword, it is irrelevant for a function declaration.

checkpatch --strict doesn't like it either 
(https://openpower.xyz/job/snowpatch/job/snowpatch-linux-checkpatch/12318//artifact/linux/checkpatch.log)

> +
>   #include <asm-generic/hugetlb.h>
>   
>   #else /* ! CONFIG_HUGETLB_PAGE */
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 33b3461d91e8..b78f660252f3 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -558,7 +558,7 @@ unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
>   	return vma_kernel_pagesize(vma);
>   }
>   
> -static int __init add_huge_page_size(unsigned long long size)
> +bool __init arch_hugetlb_valid_size(unsigned long long size)
>   {
>   	int shift = __ffs(size);
>   	int mmu_psize;
> @@ -566,20 +566,26 @@ static int __init add_huge_page_size(unsigned long long size)
>   	/* Check that it is a page size supported by the hardware and
>   	 * that it fits within pagetable and slice limits. */
>   	if (size <= PAGE_SIZE || !is_power_of_2(size))
> -		return -EINVAL;
> +		return false;
>   
>   	mmu_psize = check_and_get_huge_psize(shift);
>   	if (mmu_psize < 0)
> -		return -EINVAL;
> +		return false;
>   
>   	BUG_ON(mmu_psize_defs[mmu_psize].shift != shift);
>   
> -	/* Return if huge page size has already been setup */
> -	if (size_to_hstate(size))
> -		return 0;
> +	return true;
> +}
>   
> -	hugetlb_add_hstate(shift - PAGE_SHIFT);
> +static int __init add_huge_page_size(unsigned long long size)
> +{
> +	int shift = __ffs(size);
> +
> +	if (!arch_hugetlb_valid_size(size))
> +		return -EINVAL;
>   
> +	if (!size_to_hstate(size))
> +		hugetlb_add_hstate(shift - PAGE_SHIFT);
>   	return 0;
>   }
>   

[snip]

> diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
> index 5bfd5aef5378..51e6208fdeec 100644
> --- a/arch/x86/mm/hugetlbpage.c
> +++ b/arch/x86/mm/hugetlbpage.c
> @@ -181,16 +181,25 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
>   #endif /* CONFIG_HUGETLB_PAGE */
>   
>   #ifdef CONFIG_X86_64
> +bool __init arch_hugetlb_valid_size(unsigned long long size)
> +{
> +	if (size == PMD_SIZE)
> +		return true;
> +	else if (size == PUD_SIZE && boot_cpu_has(X86_FEATURE_GBPAGES))
> +		return true;
> +	else
> +		return false;
> +}
> +
>   static __init int setup_hugepagesz(char *opt)
>   {
> -	unsigned long ps = memparse(opt, &opt);
> -	if (ps == PMD_SIZE) {
> -		hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
> -	} else if (ps == PUD_SIZE && boot_cpu_has(X86_FEATURE_GBPAGES)) {
> -		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
> +	unsigned long long ps = memparse(opt, &opt);
> +
> +	if (arch_hugetlb_valid_size(ps)) {
> +		hugetlb_add_hstate(ilog2(ps) - PAGE_SHIFT);
>   	} else {
>   		hugetlb_bad_size();
> -		printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
> +		printk(KERN_ERR "hugepagesz: Unsupported page size %llu M\n",
>   			ps >> 20);

Nowadays we use pr_err() instead of printk.

It would also likely allow you to have everything fit on a single line.

>   		return 0;
>   	}
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index b831e9fa1a26..33343eb980d0 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -678,6 +678,13 @@ static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
>   	return &mm->page_table_lock;
>   }
>   
> +#ifndef arch_hugetlb_valid_size
> +static inline bool arch_hugetlb_valid_size(unsigned long long size)
> +{
> +	return (size == HPAGE_SIZE);

Not sure the ( ) are necessary.

> +}
> +#endif
> +
>   #ifndef hugepages_supported
>   /*
>    * Some platform decide whether they support huge pages at boot
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index d8ebd876871d..2f99359b93af 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3224,12 +3224,22 @@ static int __init hugetlb_nrpages_setup(char *s)
>   }
>   __setup("hugepages=", hugetlb_nrpages_setup);
>   
> -static int __init hugetlb_default_setup(char *s)
> +static int __init default_hugepagesz_setup(char *s)
>   {
> -	default_hstate_size = memparse(s, &s);
> +	unsigned long long size;

Why unsigned long long ?

default_hstate_size is long.

I can't imagine 32 bits platforms having a hugepage with a 64 bits size.

> +	char *saved_s = s;
> +
> +	size = memparse(s, &s);

The updated s is not reused after that so you can pass NULL instead of 
&s and then you don't need the saved_s.

> +
> +	if (!arch_hugetlb_valid_size(size)) {
> +		pr_err("HugeTLB: unsupported default_hugepagesz %s\n", saved_s);
> +		return 0;
> +	}
> +
> +	default_hstate_size = size;
>   	return 1;
>   }
> -__setup("default_hugepagesz=", hugetlb_default_setup);
> +__setup("default_hugepagesz=", default_hugepagesz_setup);
>   
>   static unsigned int cpuset_mems_nr(unsigned int *array)
>   {
> 


Christophe