On Fri, Aug 04, 2017 at 10:52:45AM +0800, Dou Liyang wrote: >Hi chao > >At 08/04/2017 10:01 AM, Chao Fan wrote: >> On Fri, Aug 04, 2017 at 09:37:14AM +0800, Dou Liyang wrote: >> > Hi Chao,Baoquan >> > >> > At 08/04/2017 07:49 AM, Baoquan He wrote: >> > > On 08/03/17 at 08:24pm, Chao Fan wrote: >> > > > It's almost another "mem=". >> > > >> > >> > No, it is different. >> > >> > See Documentation/kernel-parameters: >> > >> > "mem=" will force usage of a specific amount of memory and kernel will >> > not see the whole system memory. >> > >> > But "movable_node=" will not do that. >> > >> > >> > > Then why not using 'mem=' directly? >> > > >> > >> > Before answer this question, let's first discuss why the users want to >> > replace "mem=" with "movable_node" when they hope to support NUMA node >> > hot-plug. >> > >> > I guess the real reason is that: >> > >> > When booting up the system, We should have the whole memory not just >> > the un-hotpluggable memory which restrict by "mem=", eg: >> > >> > we boot up kernel with 4 node: >> > >> > node 0 size: 1024 MB immovable >> > node 1 size: 1024 MB movable >> > node 2 size: 1024 MB movable >> > node 3 size: 1024 MB movable >> > >> > If we use "mem=1024M" in the command line, we just can use 1G memory. >> > But actually, we should have 4G normally. >> > >> > Above is also one reason for why not using 'mem=' directly. Following >> > is other reasons: >> > >> Hi Dou, >> >> > 1). each kernel option has its own role, we'd better misuse them. >> >> I guess you mean "we'd better not misuse them" >> > >Oops, yes, thanks! > >> > 2). movable_node is used as a boot-time switch to make nodes movable >> > or not, it should consider any situations, such as KASLR. >> >> Yes, then in my understanding, as for this issue, you will leave both >> "movable_node" and "movable_node=nn[KMG]" in kernel option, right? > >Yes, Both. > >> If so, then what will happen when only "movable_node" specified >> without "movable_node=nn[KMG]"? > >If the system does not support KASLR and has movable node, people can >use movable_node directly or use movable_node=nn[KMG], but the >parameter "nn" will useless. > >If the system supports both KASLR and movable node, please use >movable_node=nn[KMG] instead of movable_node.
Hi Dou, So many thanks for your explaination. I got it, with both KASLR and movable_node feature specified, you suggest users use "movable_node=nn[KMG]" but not "movable_node". Thanks, Chao Fan > >Thanks, > dou. > >> If I misunderstand it, please let me know. >> >> Thanks, >> Chao Fan >> >> > >> > >> > Thanks, >> > dou. >> > >> > > > >> > > > On Thu, Aug 03, 2017 at 08:17:21PM +0800, Dou Liyang wrote: >> > > > > movable_node is a boot-time switch to make hot-pluggable memory >> > > > > NUMA nodes to be movable. This option is based on an assumption >> > > > > that any node which the kernel resides in is defined as >> > > > > un-hotpluggable. Linux can allocates memory near the kernel image >> > > > > to try the best to keep the kernel away from hotpluggable memory >> > > > > in the same NUMA node. So other nodes can be movable. >> > > > > >> > > > > But, KASLR doesn't know which node is un-hotpluggable, the all >> > > > > hotpluggable memory ranges is recorded in ACPI SRAT table, SRAT >> > > > > is not parsed. So, KASLR may randomize the kernel in a movable >> > > > > node which will be immovable. >> > > > > >> > > > > Extend movable_node option to restrict kernel to be randomized in >> > > > > immovable nodes by adding a parameter. this parameter sets up >> > > > > the boundaries between the movable nodes and immovable nodes. >> > > > > >> > > > > Reported-by: Chao Fan <[email protected]> >> > > > > Signed-off-by: Dou Liyang <[email protected]> >> > > > > --- >> > > > > Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++-- >> > > > > arch/x86/boot/compressed/kaslr.c | 19 >> > > > > ++++++++++++++++--- >> > > > > 2 files changed, 25 insertions(+), 5 deletions(-) >> > > > > >> > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt >> > > > > b/Documentation/admin-guide/kernel-parameters.txt >> > > > > index d9c171c..44c7e33 100644 >> > > > > --- a/Documentation/admin-guide/kernel-parameters.txt >> > > > > +++ b/Documentation/admin-guide/kernel-parameters.txt >> > > > > @@ -2305,7 +2305,8 @@ >> > > > > mousedev.yres= [MOUSE] Vertical screen resolution, used for >> > > > > devices >> > > > > reporting absolute coordinates, such as tablets >> > > > > >> > > > > - movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter >> > > > > + movablecore=nn[KMG] >> > > > > + [KNL,X86,IA-64,PPC] This parameter >> > > > > is similar to kernelcore except it specifies the >> > > > > amount of memory used for migratable >> > > > > allocations. >> > > > > If both kernelcore and movablecore is specified, >> > > > > @@ -2315,12 +2316,18 @@ >> > > > > that the amount of memory usable for all >> > > > > allocations >> > > > > is not too small. >> > > > > >> > > > > - movable_node [KNL] Boot-time switch to make hotplugable >> > > > > memory >> > > > > + movable_node [KNL] Boot-time switch to make hot-pluggable >> > > > > memory >> > > > > NUMA nodes to be movable. This means that the >> > > > > memory >> > > > > of such nodes will be usable only for movable >> > > > > allocations which rules out almost all kernel >> > > > > allocations. Use with caution! >> > > > > >> > > > > + movable_node=nn[KMG] >> > > > > + [KNL] Extend movable_node to work well with >> > > > > KASLR. This >> > > > > + parameter is the boundaries between the movable >> > > > > nodes >> > > > > + and immovable nodes, the memory which exceeds >> > > > > it will >> > > > > + be regarded as hot-pluggable. >> > > > > + >> > > > > MTD_Partition= [MTD] >> > > > > Format: <name>,<region-number>,<size>,<offset> >> > > > > >> > > > > diff --git a/arch/x86/boot/compressed/kaslr.c >> > > > > b/arch/x86/boot/compressed/kaslr.c >> > > > > index 91f27ab..7e2351b 100644 >> > > > > --- a/arch/x86/boot/compressed/kaslr.c >> > > > > +++ b/arch/x86/boot/compressed/kaslr.c >> > > > > @@ -89,7 +89,10 @@ struct mem_vector { >> > > > > static bool memmap_too_large; >> > > > > >> > > > > >> > > > > -/* Store memory limit specified by "mem=nn[KMG]" or >> > > > > "memmap=nn[KMG]" */ >> > > > > +/* >> > > > > + * Store memory limit specified by the following situations: >> > > > > + * "mem=nn[KMG]" or "memmap=nn[KMG]" or "movable_node=nn[KMG]" >> > > > > + */ >> > > > > unsigned long long mem_limit = ULLONG_MAX; >> > > > > >> > > > > >> > > > > @@ -212,7 +215,8 @@ static int handle_mem_memmap(void) >> > > > > char *param, *val; >> > > > > u64 mem_size; >> > > > > >> > > > > - if (!strstr(args, "memmap=") && !strstr(args, "mem=")) >> > > > > + if (!strstr(args, "memmap=") && !strstr(args, "mem=") && >> > > > > + !strstr(args, "movable_node=")) >> > > > > return 0; >> > > > > >> > > > > tmp_cmdline = malloc(len + 1); >> > > > > @@ -247,7 +251,16 @@ static int handle_mem_memmap(void) >> > > > > free(tmp_cmdline); >> > > > > return -EINVAL; >> > > > > } >> > > > > - mem_limit = mem_size; >> > > > > + mem_limit = mem_limit > mem_size ? mem_size : >> > > > > mem_limit; >> > > > > + } else if (!strcmp(param, "movable_node")) { >> > > > > + char *p = val; >> > > > > + >> > > > > + mem_size = memparse(p, &p); >> > > > > + if (mem_size == 0) { >> > > > > + free(tmp_cmdline); >> > > > > + return -EINVAL; >> > > > > + } >> > > > > + mem_limit = mem_limit > mem_size ? mem_size : >> > > > > mem_limit; >> > > > > } >> > > > > } >> > > > > >> > > > > -- >> > > > > 2.5.5 >> > > > > >> > > > >> > > > >> > > >> > > >> > > >>
