Messages in this thread | | | Subject | Re: [PATCH] x86/boot/KASLR: Extend movable_node option for KASLR | From | Dou Liyang <> | Date | Fri, 4 Aug 2017 10:42:51 +0800 |
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Hi Baoquan,
At 08/04/2017 10:00 AM, Baoquan He wrote: > On 08/04/17 at 09:37am, 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. > > So do you have assumption on the order of immovable nodes and movable > nodes? E.g above your example of nodes, immovable nodes have to be the > lowest address. Is this required by the current hot-plug memory code? >
Wow! So great, It seems this is required by the hot-plug memory code.
yesterday, I tested the patch in Qemu with 4 node and each time I used different node as immovable node. But no matter what node I used, the immovable nodes always had the lowest address.
I am not familiar with memory, I am investigating this and I am going to apply for a physical machine with movable nodes to check. :)
Thanks,
dou. >> >> Above is also one reason for why not using 'mem=' directly. Following >> is other reasons: >> >> 1). each kernel option has its own role, we'd better misuse them. >> 2). movable_node is used as a boot-time switch to make nodes movable >> or not, it should consider any situations, such as KASLR. >> >> >> 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. > > And here you mentioned boundaries, means not only one boundary, so how > do you handle the case movable nodes and immovable nodes alternate to be > placed? > > I mean, are you sure the current hot-plug memory code require immovable > node has to be the first node and there's only one immovable node or > there are several immovable node but they are the first few nodes? > > If yes, then this patch looks good to me, I would like to ack it. > > Thanks > Baoquan > >>>>> >>>>> Reported-by: Chao Fan <fanc.fnst@cn.fujitsu.com> >>>>> Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com> >>>>> --- >>>>> 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 >>>>> >>>> >>>> >>> >>> >>> >> >> > > >
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