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s390/boot: always align vmalloc area on segment boundary

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The size of vmalloc area depends from various factors
on boot and could be set to:

1. Default size as determined by VMALLOC_DEFAULT_SIZE macro;
2. One half of the virtual address space not occupied by
   modules and fixed mappings;
3. The size provided by user with vmalloc= kernel command
   line parameter;

In cases [1] and [2] the vmalloc area base address is aligned
on Region3 table type boundary, while in case [3] in might get
aligned on page boundary.

Limit the waste of page tables and always align vmalloc area
size and base address on segment boundary.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Alexander Gordeev 2023-07-16 10:56:00 +02:00
parent d12292fdea
commit 65f8780e2d
2 changed files with 3 additions and 2 deletions
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2
arch/s390/boot/ipl_parm.c
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@ -274,7 +274,7 @@ void parse_boot_command_line(void)
memory_limit = round_down(memparse(val, NULL), PAGE_SIZE);
if (!strcmp(param, "vmalloc") && val) {
vmalloc_size = round_up(memparse(val, NULL), PAGE_SIZE);
vmalloc_size = round_up(memparse(val, NULL), _SEGMENT_SIZE);
vmalloc_size_set = 1;
}

3
arch/s390/boot/startup.c
View file

@ -255,7 +255,8 @@ static unsigned long setup_kernel_memory_layout(void)
VMALLOC_END = MODULES_VADDR;
/* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */
vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE));
vsize = round_down(VMALLOC_END / 2, _SEGMENT_SIZE);
vmalloc_size = min(vmalloc_size, vsize);
VMALLOC_START = VMALLOC_END - vmalloc_size;
/* split remaining virtual space between 1:1 mapping & vmemmap array */