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Date: Wed, 9 Aug 2017 22:44:55 +0800
From: Dou Liyang <douly.fnst@...fujitsu.com>
To: YASUAKI ISHIMATSU <yasu.isimatu@...il.com>,
Baoquan He <bhe@...hat.com>
CC: Chao Fan <fanc.fnst@...fujitsu.com>,
<linux-kernel@...r.kernel.org>, <x86@...nel.org>,
<tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
<keescook@...omium.org>, <dyoung@...hat.com>, <arnd@...db.de>,
<dave.jiang@...el.com>, <indou.takao@...fujitsu.com>,
<izumi.taku@...fujitsu.com>
Subject: Re: [PATCH] x86/boot/KASLR: Extend movable_node option for KASLR
Hi YASUAKI,
[...]
>>>>>>
>>>>>> 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. :)
>>>
>>
>> Cc YASUAKI ISHIMATSU
>>
>> could you give us some help!
>>
>>> Great, thanks for your effort. I asked because this question confuses me
>>> and I know FJ ever focusd on the memory hot-plug implementation and
>>> continue working on that, it must be easier for you to consult your
>>> co-workers who ever worked on this. For normal kernel, seems it has
>>> to be that normal zone is on immovable node, namely node0. But what if
>>> people modified bootloader to locate kernel onto the last node and
>>> configure efi firmware to make the last node un-hot-plugable? I believe
>>> both of these can be done. Is this allowed? memory hot-plug has a
>>> requirement about the order of immovable node? And how many immovable
>>> nodes can we have? I have an slides FJ published, didn't find info about
>>> these.
>
> I read your patch. And I think what Baoquan wrote is right. The patch does
> care of only your server. As he wrote, if a server wants to build immovable
> node onto last node, the patch cannot handle such configuration.
>
Thanks for your reviewing. it is reasonable. I will keep in my mind.
But, I am not sure that when we boot up a system with the following 4
nodes, does the BOIS(ACPI firmware) map the immovable node RAM from the
lowest address first?
node 0 size: 1024 MB immovable
node 1 size: 1024 MB movable
node 2 size: 1024 MB movable
node 3 size: 1024 MB immovable
the order of the physical RAM maps may be node 0, 3, 1, 2.
Thanks,
dou,
> Thanks,
> Yasuaki Ishimatsu
>
>>>
>>
>> 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@...fujitsu.com>
>>>>>>>>> Signed-off-by: Dou Liyang <douly.fnst@...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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