linux-kernel - Re: [PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <551B5F17.4070100@jp.fujitsu.com>
Date:	Wed, 1 Apr 2015 11:59:35 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Gu Zheng <guz.fnst@...fujitsu.com>
CC:	<linux-kernel@...r.kernel.org>, <tj@...nel.org>,
	<laijs@...fujitsu.com>, <isimatu.yasuaki@...fujitsu.com>,
	<tangchen@...fujitsu.com>, <izumi.taku@...fujitsu.com>
Subject: Re: [PATCH 1/2] x86/cpu hotplug: make apicid <--> cpuid mapping persistent

On 2015/03/30 18:58, Gu Zheng wrote:
> Hi Kame-san,
> 
> On 03/27/2015 12:31 AM, Kamezawa Hiroyuki wrote:
> 
>> On 2015/03/26 13:55, Gu Zheng wrote:
>>> Hi Kame-san,
>>> On 03/26/2015 11:19 AM, Kamezawa Hiroyuki wrote:
>>>
>>>> On 2015/03/26 11:17, Gu Zheng wrote:
>>>>> Previously, we build the apicid <--> cpuid mapping when the cpu is present, but
>>>>> the relationship will be changed if the cpu/node hotplug happenned, because we
>>>>> always choose the first free cpuid for the hot added cpu (whether it is new-add
>>>>> or re-add), so this the cpuid <--> node mapping changed if node hot plug
>>>>> occurred, and it causes the wq sub-system allocation failture:
>>>>>      ==
>>>>>         SLUB: Unable to allocate memory on node 2 (gfp=0x80d0)
>>>>>          cache: kmalloc-192, object size: 192, buffer size: 192, default
>>>>> order:
>>>>>        1, min order: 0
>>>>>          node 0: slabs: 6172, objs: 259224, free: 245741
>>>>>          node 1: slabs: 3261, objs: 136962, free: 127656
>>>>>      ==
>>>>> So here we build the persistent [lapic id] <--> cpuid mapping when the cpu first
>>>>> present, and never change it.
>>>>>
>>>>> Suggested-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>>>> Signed-off-by: Gu Zheng <guz.fnst@...fujitsu.com>
>>>>> ---
>>>>>     arch/x86/kernel/apic/apic.c |   31 ++++++++++++++++++++++++++++++-
>>>>>     1 files changed, 30 insertions(+), 1 deletions(-)
>>>>>
>>>>> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
>>>>> index ad3639a..d539ebc 100644
>>>>> --- a/arch/x86/kernel/apic/apic.c
>>>>> +++ b/arch/x86/kernel/apic/apic.c
>>>>> @@ -2038,6 +2038,30 @@ void disconnect_bsp_APIC(int virt_wire_setup)
>>>>>     	apic_write(APIC_LVT1, value);
>>>>>     }
>>>>>     
>>>>> +/*
>>>>> + * Logic cpu number(cpuid) to local APIC id persistent mappings.
>>>>> + * Do not clear the mapping even if cpu hot removed.
>>>>> + * */
>>>>> +static int apicid_to_x86_cpu[MAX_LOCAL_APIC] = {
>>>>> +	[0 ... MAX_LOCAL_APIC - 1] = -1,
>>>>> +};
>>>>
>>>>
>>>> This patch cannot handle x2apic, which is 32bit.
>>>
>>> IMO, if the apicid is too big (larger than MAX_LOCAL_APIC), we will skip
>>> generating a logic cpu number for it, so it seems no problem here.
>>>
>> you mean MAX_LOCAL_APIC=32768 ? ....isn't it too wasting ?
> 
> I use the big array here to keep the same format with the existed ones:
> int apic_version[MAX_LOCAL_APIC];
> 
> s16 __apicid_to_node[MAX_LOCAL_APIC] = {
> 	[0 ... MAX_LOCAL_APIC-1] = NUMA_NO_NODE
> };
> Or we should also say "NO" to them?

This will not survive when someone try to enlarge MAX_LOCAL_APIC for
introdcing new cpu model because x2apic is 32bit by definition.

Please create long surviving infrastructure.

Thanks,
-Kame





--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/