diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 13 | ||||
| -rw-r--r-- | mm/memory_hotplug.c | 8 |
2 files changed, 18 insertions, 3 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2d31d811a52d..86aae1fa099a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2573,13 +2573,22 @@ For details see: Documentation/admin-guide/hw-vuln/mds.rst mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory - Amount of memory to be used when the kernel is not able - to see the whole system memory or for test. + Amount of memory to be used in cases as follows: + + 1 for test; + 2 when the kernel is not able to see the whole system memory; + 3 memory that lies after 'mem=' boundary is excluded from + the hypervisor, then assigned to KVM guests. + [X86] Work as limiting max address. Use together with memmap= to avoid physical address space collisions. Without memmap= PCI devices could be placed at addresses belonging to unused RAM. + Note that this only takes effects during boot time since + in above case 3, memory may need be hot added after boot + if system memory of hypervisor is not sufficient. + mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel memory. diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 005eab3411e5..d6f813cc12c1 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -105,7 +105,13 @@ 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) + /* + * Make sure value parsed from 'mem=' only restricts memory adding + * while booting, so that memory hotplug won't be impacted. Please + * refer to document of 'mem=' in kernel-parameters.txt for more + * details. + */ + if (start + size > max_mem_size && system_state < SYSTEM_RUNNING) return ERR_PTR(-E2BIG); /* |