[PATCH v2] arm64: mm: Increase MODULES_VSIZE to 2GB

From: Shanker Donthineni
Date: Thu Mar 30 2023 - 10:04:58 EST

The allocation of modules occurs in two regions. The first region
is MODULES_VSIZE, which is 128MB in size and shared with the core
kernel when the KASLR feature is unavailable or disabled through
a boot parameter. The second region, which is 2GB in size, is
shared with the other vmalloc callers. Depending on the size of
the core kernel, the 128MB region may quickly fill up after
loading a few modules, causing the system to switch to the 2GB
region. Unfortunately, even the 2GB region can run out of space
if previously loaded modules and other kernel subsystems consume
the entire area, leaving no space for additional modules.

This issue usually occurs when the system has a large number of
CPU cores, PCIe host-brigde controllers, and I/O devices. For
instance, the ECAM region of one host-bridge controller can use
up to 256MB of vmalloc space, while eight controllers can occupy
the entire 2GB.

To address this problem, a possible solution would be to increase
the MODULES_VSIZE to 2GB. This would improve the system's ability
to accommodate a greater number of dynamically loaded modules and
drivers when KASLR is not enabled. However, prior to switching to
the 2GB region, it is advisable to allocate modules within the
128MB space that covers the core kernel, in order to benefit from
the direct branches.

Signed-off-by: Shanker Donthineni <sdonthineni@xxxxxxxxxx>
---
Changes since v1:
- Included Ard's recommendations.
- Revised the commit message.

dmesg:
On a NVIDIA T241 system with Ubuntu-22.04, hitting boot failures
due to vmalloc/vmap allocation errors when loading modules.

[ 64.181308] ipmi_ssif: IPMI SSIF Interface driver
[ 64.184494] usbcore: registered new interface driver r8152
[ 64.242492] vmap allocation for size 393216 failed: use vmalloc=<size> to increase size
[ 64.242499] systemd-udevd: vmalloc error: size 327680, vm_struct allocation failed, mode:0xcc0(GFP_KERNEL), nodemask=(null),cpuset=/,mems_allowed=0-3
[ 64.242510] CPU: 32 PID: 2910 Comm: systemd-udevd Tainted: G OE 6.2-generic-64k
[ 64.242513] Hardware name: NVIDIA T241, BIOS v1.1.0 2023-03-18T21:32:31+00:00
[ 64.242515] Call trace:
[ 64.242516] dump_backtrace+0xe0/0x130
[ 64.242523] show_stack+0x20/0x60
[ 64.242525] dump_stack_lvl+0x68/0x84
[ 64.242530] dump_stack+0x18/0x34
[ 64.242532] warn_alloc+0x11c/0x1b0
[ 64.242537] __vmalloc_node_range+0xe0/0x20c
[ 64.242540] module_alloc+0x118/0x160
[ 64.242543] move_module+0x2c/0x190
[ 64.242546] layout_and_allocate+0xfc/0x160
[ 64.242548] load_module+0x260/0xbc4
[ 64.242549] __do_sys_finit_module+0xac/0x130
[ 64.242551] __arm64_sys_finit_module+0x28/0x34
[ 64.242552] invoke_syscall+0x78/0x100
[ 64.242553] el0_svc_common.constprop.0+0x170/0x194
[ 64.242555] do_el0_svc+0x38/0x4c
[ 64.242556] el0_svc+0x2c/0xc0
[ 64.242558] el0t_64_sync_handler+0xbc/0x13c
[ 64.242560] el0t_64_sync+0x1a0/0x1a4

Documentation/arm64/memory.rst | 8 ++++----
arch/arm64/include/asm/memory.h | 2 +-
arch/arm64/kernel/module.c | 2 +-
3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Documentation/arm64/memory.rst b/Documentation/arm64/memory.rst
index 2a641ba7be3b..55a55f30eed8 100644
--- a/Documentation/arm64/memory.rst
+++ b/Documentation/arm64/memory.rst
@@ -33,8 +33,8 @@ AArch64 Linux memory layout with 4KB pages + 4 levels (48-bit)::
0000000000000000 0000ffffffffffff 256TB user
ffff000000000000 ffff7fffffffffff 128TB kernel logical memory map
[ffff600000000000 ffff7fffffffffff] 32TB [kasan shadow region]
- ffff800000000000 ffff800007ffffff 128MB modules
- ffff800008000000 fffffbffefffffff 124TB vmalloc
+ ffff800000000000 ffff80007fffffff 2GB modules
+ ffff800080000000 fffffbffefffffff 124TB vmalloc
fffffbfff0000000 fffffbfffdffffff 224MB fixed mappings (top down)
fffffbfffe000000 fffffbfffe7fffff 8MB [guard region]
fffffbfffe800000 fffffbffff7fffff 16MB PCI I/O space
@@ -50,8 +50,8 @@ AArch64 Linux memory layout with 64KB pages + 3 levels (52-bit with HW support):
0000000000000000 000fffffffffffff 4PB user
fff0000000000000 ffff7fffffffffff ~4PB kernel logical memory map
[fffd800000000000 ffff7fffffffffff] 512TB [kasan shadow region]
- ffff800000000000 ffff800007ffffff 128MB modules
- ffff800008000000 fffffbffefffffff 124TB vmalloc
+ ffff800000000000 ffff80007fffffff 2GB modules
+ ffff800080000000 fffffbffefffffff 124TB vmalloc
fffffbfff0000000 fffffbfffdffffff 224MB fixed mappings (top down)
fffffbfffe000000 fffffbfffe7fffff 8MB [guard region]
fffffbfffe800000 fffffbffff7fffff 16MB PCI I/O space
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 78e5163836a0..b58c3127323e 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -46,7 +46,7 @@
#define KIMAGE_VADDR (MODULES_END)
#define MODULES_END (MODULES_VADDR + MODULES_VSIZE)
#define MODULES_VADDR (_PAGE_END(VA_BITS_MIN))
-#define MODULES_VSIZE (SZ_128M)
+#define MODULES_VSIZE (SZ_2G)
#define VMEMMAP_START (-(UL(1) << (VA_BITS - VMEMMAP_SHIFT)))
#define VMEMMAP_END (VMEMMAP_START + VMEMMAP_SIZE)
#define PCI_IO_END (VMEMMAP_START - SZ_8M)
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index 5af4975caeb5..b4affe775f23 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -37,7 +37,7 @@ void *module_alloc(unsigned long size)
/* don't exceed the static module region - see below */
module_alloc_end = MODULES_END;

- p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
+ p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_end - SZ_128M,
module_alloc_end, gfp_mask, PAGE_KERNEL, VM_DEFER_KMEMLEAK,
NUMA_NO_NODE, __builtin_return_address(0));

--
2.25.1