[PATCH AUTOSEL 6.6 01/19] s390/boot: always align vmalloc area on segment boundary

Sasha Levin
2024-01-16T01:05:35Z

From: Alexander Gordeev <agordeev@linux.ibm.com>

[ Upstream commit 65f8780e2d70257200547b5a7654974aa7c37ce1 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/boot/ipl_parm.c | 2 +-
arch/s390/boot/startup.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/s390/boot/ipl_parm.c b/arch/s390/boot/ipl_parm.c
index 7b7521762633..4230144645bc 100644
--- a/arch/s390/boot/ipl_parm.c
+++ b/arch/s390/boot/ipl_parm.c
@@ -272,7 +272,7 @@ 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;
}

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index d3e48bd9c394..d08db5df6091 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -212,7 +212,8 @@ 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 */
--
2.43.0