On 09.12.19 11:07, Michal Hocko wrote:
On Fri 06-12-19 23:05:24, Baoquan He wrote:
In commit 357b4da50a62 ("x86: respect memory size limiting via mem=
parameter") a global varialbe global max_mem_size is added to store
the value which is parsed from 'mem= '. This truly stops those
DIMM from being added into system memory during boot.
However, it also limits the later memory hotplug functionality. Any
memory board can't be hot added any more if its region is beyond the
max_mem_size. System will print error like below:
[ 216.387164] acpi PNP0C80:02: add_memory failed
[ 216.389301] acpi PNP0C80:02: acpi_memory_enable_device() error
[ 216.392187] acpi PNP0C80:02: Enumeration failure
>From document of 'mem =' parameter, it should be a restriction during
boot, but not impact the system memory adding/removing after booting.
mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
So fix it by also checking if it's during SYSTEM_BOOTING stage when
restrict memory adding. Otherwise, skip the restriction.
Could you be more specific about why the boot vs. later hotplug makes
any difference? The documentation is explicit about the boot time but
considering this seems to be like that since ever I strongly suspect
that this is just an omission.
Btw. how have you tested the situation fixed by 357b4da50a62?
I guess he hasn't.
The backtrace of the problem at that time was:
[ 8321.876844] [<ffffffff81019ab9>] dump_trace+0x59/0x340
[ 8321.882683] [<ffffffff81019e8a>] show_stack_log_lvl+0xea/0x170
[ 8321.889298] [<ffffffff8101ac31>] show_stack+0x21/0x40
[ 8321.895043] [<ffffffff81319530>] dump_stack+0x5c/0x7c
[ 8321.900779] [<ffffffff8107fbf1>] warn_slowpath_common+0x81/0xb0
[ 8321.907482] [<ffffffff81009f54>] xen_alloc_pte+0x1d4/0x390
[ 8321.913718] [<ffffffff81064950>]
pmd_populate_kernel.constprop.6+0x40/0x80
[ 8321.921498] [<ffffffff815ef0a8>] phys_pmd_init+0x210/0x255
[ 8321.927724] [<ffffffff815ef2c7>] phys_pud_init+0x1da/0x247
[ 8321.933951] [<ffffffff815efb81>] kernel_physical_mapping_init+0xf5/0x1d4
[ 8321.941533] [<ffffffff815ebc7d>] init_memory_mapping+0x18d/0x380
[ 8321.948341] [<ffffffff810647f9>] arch_add_memory+0x59/0xf0
[ 8321.954570] [<ffffffff815eceed>] add_memory_resource+0x8d/0x160
[ 8321.961283] [<ffffffff815ecff2>] add_memory+0x32/0xf0
[ 8321.967025] [<ffffffff813e1c91>] acpi_memory_device_add+0x131/0x2e0
[ 8321.974128] [<ffffffff8139f752>] acpi_bus_attach+0xe2/0x190
[ 8321.980453] [<ffffffff8139f6ce>] acpi_bus_attach+0x5e/0x190
[ 8321.986778] [<ffffffff8139f6ce>] acpi_bus_attach+0x5e/0x190
[ 8321.993103] [<ffffffff8139f6ce>] acpi_bus_attach+0x5e/0x190
[ 8321.999428] [<ffffffff813a1157>] acpi_bus_scan+0x37/0x70
[ 8322.005461] [<ffffffff81fba955>] acpi_scan_init+0x77/0x1b4
[ 8322.011690] [<ffffffff81fba70c>] acpi_init+0x297/0x2b3
[ 8322.017530] [<ffffffff8100213a>] do_one_initcall+0xca/0x1f0
[ 8322.023855] [<ffffffff81f74266>] kernel_init_freeable+0x194/0x226
[ 8322.030760] [<ffffffff815eb1ba>] kernel_init+0xa/0xe0
[ 8322.036503] [<ffffffff815f7bc5>] ret_from_fork+0x55/0x80
So this patch would break it again.
I'd recommend ...
Fixes: 357b4da50a62 ("x86: respect memory size limiting via mem= parameter")
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
---
mm/memory_hotplug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 55ac23ef11c1..5466a0a00901 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -105,7 +105,7 @@ static struct resource *register_memory_resource(u64 start, u64 size)
unsigned long flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
char *resource_name = "System RAM";
- if (start + size > max_mem_size)
+ if (start + size > max_mem_size && system_state == SYSTEM_BOOTING)
... changing this to: ... && system_state != SYSTEM_RUNNING
With that you can add my:
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Juergen
