linux-kernel - Re: [PATCH 1/1] selftests: mm: hugepage-vmemmap fails on 64K page size systems.

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Message-Id: <20240110075351.f4b6f43e31629ddcb96503cc@linux-foundation.org>
Date: Wed, 10 Jan 2024 07:53:51 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Donet Tom <donettom@...ux.vnet.ibm.com>
Cc: linux-kselftest@...r.kernel.org, Aneesh Kumar
 <aneesh.kumar@...ux.ibm.com>, linux-mm@...ck.org,
 linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, Geetika
 Moolchandani <geetika@...ux.ibm.com>, Muchun Song <muchun.song@...ux.dev>
Subject: Re: [PATCH 1/1] selftests: mm: hugepage-vmemmap fails on 64K page
 size systems.

(cc Muchun)
On Wed, 10 Jan 2024 14:03:35 +0530 Donet Tom <donettom@...ux.vnet.ibm.com> wrote:

> The kernel sefltest mm/hugepage-vmemmap fails on architectures
> which has different page size other than 4K. In hugepage-vmemmap
> page size used is 4k so the pfn calculation will go wrong on systems
> which has different page size .The length of MAP_HUGETLB memory must
> be hugepage aligned but in hugepage-vmemmap map length is 2M so this
> will not get aligned if the system has differnet hugepage size.
> 
> Added  psize() to get the page size and default_huge_page_size() to
> get the default hugepage size at run time, hugepage-vmemmap test pass
> on powerpc with 64K page size and x86 with 4K page size.
> 
> Result on powerpc without patch (page size 64K)
> *# ./hugepage-vmemmap
> Returned address is 0x7effff000000 whose pfn is 0
> Head page flags (100000000) is invalid
> check_page_flags: Invalid argument
> *#
> 
> Result on powerpc with patch (page size 64K)
> *# ./hugepage-vmemmap
> Returned address is 0x7effff000000 whose pfn is 600
> *#
> 
> Result on x86 with patch (page size 4K)
> *# ./hugepage-vmemmap
> Returned address is 0x7fc7c2c00000 whose pfn is 1dac00
> *#
> 
> Signed-off-by: Donet Tom <donettom@...ux.vnet.ibm.com>
> Reported-by : Geetika Moolchandani (geetika@...ux.ibm.com)
> Tested-by : Geetika Moolchandani (geetika@...ux.ibm.com)

I'll add 

Fixes: b147c89cd429 ("selftests: vm: add a hugetlb test case")
Cc: <stable@...r.kernel.org>

> 
> diff --git a/tools/testing/selftests/mm/hugepage-vmemmap.c b/tools/testing/selftests/mm/hugepage-vmemmap.c
> index 5b354c209e93..894d28c3dd47 100644
> --- a/tools/testing/selftests/mm/hugepage-vmemmap.c
> +++ b/tools/testing/selftests/mm/hugepage-vmemmap.c
> @@ -10,10 +10,7 @@
>  #include <unistd.h>
>  #include <sys/mman.h>
>  #include <fcntl.h>
> -
> -#define MAP_LENGTH		(2UL * 1024 * 1024)
> -
> -#define PAGE_SIZE		4096
> +#include "vm_util.h"
>  
>  #define PAGE_COMPOUND_HEAD	(1UL << 15)
>  #define PAGE_COMPOUND_TAIL	(1UL << 16)
> @@ -39,6 +36,9 @@
>  #define MAP_FLAGS		(MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
>  #endif
>  
> +static size_t pagesize;
> +static size_t maplength;
> +
>  static void write_bytes(char *addr, size_t length)
>  {
>  	unsigned long i;
> @@ -56,7 +56,7 @@ static unsigned long virt_to_pfn(void *addr)
>  	if (fd < 0)
>  		return -1UL;
>  
> -	lseek(fd, (unsigned long)addr / PAGE_SIZE * sizeof(pagemap), SEEK_SET);
> +	lseek(fd, (unsigned long)addr / pagesize * sizeof(pagemap), SEEK_SET);
>  	read(fd, &pagemap, sizeof(pagemap));
>  	close(fd);
>  
> @@ -86,7 +86,7 @@ static int check_page_flags(unsigned long pfn)
>  	 * this also verifies kernel has correctly set the fake page_head to tail
>  	 * while hugetlb_free_vmemmap is enabled.
>  	 */
> -	for (i = 1; i < MAP_LENGTH / PAGE_SIZE; i++) {
> +	for (i = 1; i < maplength / pagesize; i++) {
>  		read(fd, &pageflags, sizeof(pageflags));
>  		if ((pageflags & TAIL_PAGE_FLAGS) != TAIL_PAGE_FLAGS ||
>  		    (pageflags & HEAD_PAGE_FLAGS) == HEAD_PAGE_FLAGS) {
> @@ -106,18 +106,25 @@ int main(int argc, char **argv)
>  	void *addr;
>  	unsigned long pfn;
>  
> -	addr = mmap(MAP_ADDR, MAP_LENGTH, PROT_READ | PROT_WRITE, MAP_FLAGS, -1, 0);
> +	pagesize  = psize();
> +	maplength = default_huge_page_size();
> +	if (!maplength) {
> +		printf("Unable to determine huge page size\n");
> +		exit(1);
> +	}
> +
> +	addr = mmap(MAP_ADDR, maplength, PROT_READ | PROT_WRITE, MAP_FLAGS, -1, 0);
>  	if (addr == MAP_FAILED) {
>  		perror("mmap");
>  		exit(1);
>  	}
>  
>  	/* Trigger allocation of HugeTLB page. */
> -	write_bytes(addr, MAP_LENGTH);
> +	write_bytes(addr, maplength);
>  
>  	pfn = virt_to_pfn(addr);
>  	if (pfn == -1UL) {
> -		munmap(addr, MAP_LENGTH);
> +		munmap(addr, maplength);
>  		perror("virt_to_pfn");
>  		exit(1);
>  	}
> @@ -125,13 +132,13 @@ int main(int argc, char **argv)
>  	printf("Returned address is %p whose pfn is %lx\n", addr, pfn);
>  
>  	if (check_page_flags(pfn) < 0) {
> -		munmap(addr, MAP_LENGTH);
> +		munmap(addr, maplength);
>  		perror("check_page_flags");
>  		exit(1);
>  	}
>  
>  	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
> -	if (munmap(addr, MAP_LENGTH)) {
> +	if (munmap(addr, maplength)) {
>  		perror("munmap");
>  		exit(1);
>  	}
> -- 
> 2.43.0