[LTP] hugemmap24 failure on aarch64 with 512MB hugepages

[Jan Stancek]

On Thu, Mar 9, 2023 at 9:29 AM Li Wang <liwang@redhat.com> wrote:
>
> [Cc'ing Jan Stancek]
>
> On Wed, Mar 8, 2023 at 5:51 PM Cyril Hrubis <chrubis@suse.cz> wrote:
>>
>> Hi!
>> Looks like the hugemmap24 test fails on aarch64 with 512MB hugepages
>> since it attempts to MAP_FIXED at NULL address, any idea why aarch64 is
>> limited to 0x10000000 as slice boundary?
>
>
> It looks like a generic/random slice_boundary that tries as a
> basic gap between two available free neighbor slices.
>
> https://github.com/libhugetlbfs/libhugetlbfs/commit/8ee2462f3f6eea72067641a197214610443576b8
> https://github.com/libhugetlbfs/libhugetlbfs/commit/399cda578564bcd52553ab88827a82481b4034d1
>
> I guess it doesn't matter just to increase the size of the boundary.
> or, we can skip testing on a big page-size system like aarch64(with 512MB)
> if unable to find the free slices.
>
> Test passed from my side with patch:
>
> --- a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24.c
> +++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24.c
> @@ -37,7 +37,7 @@ static int init_slice_boundary(int fd)
>  #else
>         /* powerpc: 256MB slices up to 4GB */
>         slice_boundary = 0x00000000;
> -       slice_size = 0x10000000;
> +       slice_size = 0x100000000;

This would likely negatively impact 32-bit, as it makes slice size 4GB.

With so large hugepages it underflows mmap address, so I'd increase it, until
we start with one larger than zero:

diff --git a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24.c
b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24.c
index a465aad..9523067 100644
--- a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24.c
+++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24.c
@@ -23,7 +23,7 @@

 static int  fd = -1;
 static unsigned long slice_boundary;
-static long hpage_size, page_size;
+static unsigned long hpage_size, page_size;

 static int init_slice_boundary(int fd)
 {
@@ -40,6 +40,10 @@ static int init_slice_boundary(int fd)
        slice_size = 0x10000000;
 #endif

+       /* avoid underflow on systems with large huge pages */
+       while (slice_boundary + slice_size < 2 * hpage_size)
+               slice_boundary += slice_size;
+
        /* dummy malloc so we know where is heap */
        heap = malloc(1);
        free(heap);


Another issue however is the use of MAP_FIXED, which can stomp over
existing mappings:

[pid 48607] 04:50:51 mmap(0x20000000, 2147483648, PROT_READ,
MAP_SHARED|MAP_FIXED, 3, 0) = 0x20000000
[pid 48607] 04:50:51 munmap(0x20000000, 2147483648) = 0

test may PASS, but at the end you get:

Program terminated with signal SIGSEGV, Segmentation fault.
#0  numa_bitmask_free (bmp=0x39ae09a0) at libnuma.c:228
228             free(bmp->maskp);
(gdb) bt
#0  numa_bitmask_free (bmp=0x39ae09a0) at libnuma.c:228
#1  numa_bitmask_free (bmp=0x39ae09a0) at libnuma.c:224
#2  0x0000ffff89263360 in numa_fini () at libnuma.c:114
#3  0x0000ffff892d4cac in _dl_fini () at dl-fini.c:141
#4  0x0000ffff890d899c in __run_exit_handlers (status=status@entry=0,
listp=0xffff892105e0 <__exit_funcs>,
run_list_atexit=run_list_atexit@entry=true,
run_dtors=run_dtors@entry=true) at exit.c:108
#5  0x0000ffff890d8b1c in __GI_exit (status=status@entry=0) at exit.c:139
#6  0x000000000040ecd8 in testrun () at tst_test.c:1468
#7  fork_testrun () at tst_test.c:1592
#8  0x0000000000410728 in tst_run_tcases (argc=<optimized out>,
argv=<optimized out>, self=self@entry=0x440650 <test>) at
tst_test.c:1686
#9  0x0000000000403ef8 in main (argc=<optimized out>, argv=<optimized
out>) at ../../../../../include/tst_test.h:394

(gdb) info proc map
Mapped address spaces:

          Start Addr           End Addr       Size     Offset objfile
            0x400000           0x430000    0x30000        0x0
/root/ltp.upstream/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24
            0x430000           0x440000    0x10000    0x20000
/root/ltp.upstream/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24
            0x440000           0x450000    0x10000    0x30000
/root/ltp.upstream/testcases/kernel/mem/hugetlb/hugemmap/hugemmap24
      0xffff890a0000     0xffff89200000   0x160000        0x0
/usr/lib64/libc-2.28.so
      0xffff89200000     0xffff89210000    0x10000   0x150000
/usr/lib64/libc-2.28.so
      0xffff89210000     0xffff89220000    0x10000   0x160000
/usr/lib64/libc-2.28.so
      0xffff89220000     0xffff89240000    0x20000        0x0
/usr/lib64/libpthread-2.28.so
      0xffff89240000     0xffff89250000    0x10000    0x10000
/usr/lib64/libpthread-2.28.so
      0xffff89250000     0xffff89260000    0x10000    0x20000
/usr/lib64/libpthread-2.28.so
      0xffff89260000     0xffff89270000    0x10000        0x0
/usr/lib64/libnuma.so.1.0.0
      0xffff89270000     0xffff89280000    0x10000        0x0
/usr/lib64/libnuma.so.1.0.0
      0xffff89280000     0xffff89290000    0x10000    0x10000
/usr/lib64/libnuma.so.1.0.0
      0xffff89290000     0xffff892a0000    0x10000        0x0
/dev/shm/ltp_hugemmap24_48644 (deleted)
      0xffff892d0000     0xffff89300000    0x30000        0x0
/usr/lib64/ld-2.28.so
      0xffff89300000     0xffff89310000    0x10000    0x20000
/usr/lib64/ld-2.28.so
      0xffff89310000     0xffff89320000    0x10000    0x30000
/usr/lib64/ld-2.28.so