linux-kernel - Re: [PATCH v5 4/6] x86/mem-hotplug: Support initialize page tables in bottom-up

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Thu, 26 Sep 2013 15:57:06 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Zhang Yanfei <zhangyanfei.yes@...il.com>
CC:	"Rafael J . Wysocki" <rjw@...k.pl>, lenb@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	Tejun Heo <tj@...nel.org>, Toshi Kani <toshi.kani@...com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Thomas Renninger <trenn@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
	mina86@...a86.com, gong.chen@...ux.intel.com,
	vasilis.liaskovitis@...fitbricks.com, lwoodman@...hat.com,
	Rik van Riel <riel@...hat.com>, jweiner@...hat.com,
	prarit@...hat.com, "x86@...nel.org" <x86@...nel.org>,
	linux-doc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>, linux-acpi@...r.kernel.org,
	imtangchen@...il.com, Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH v5 4/6] x86/mem-hotplug: Support initialize page tables in bottom-up

Can we put this in a common header somewhere?

Andrew Morton <akpm@...ux-foundation.org> wrote:
>On Wed, 25 Sep 2013 02:30:51 +0800 Zhang Yanfei
><zhangyanfei.yes@...il.com> wrote:
>
>> From: Tang Chen <tangchen@...fujitsu.com>
>> 
>> The Linux kernel cannot migrate pages used by the kernel. As a
>> result, kernel pages cannot be hot-removed. So we cannot allocate
>> hotpluggable memory for the kernel.
>> 
>> In a memory hotplug system, any numa node the kernel resides in
>> should be unhotpluggable. And for a modern server, each node could
>> have at least 16GB memory. So memory around the kernel image is
>> highly likely unhotpluggable.
>> 
>> ACPI SRAT (System Resource Affinity Table) contains the memory
>> hotplug info. But before SRAT is parsed, memblock has already
>> started to allocate memory for the kernel. So we need to prevent
>> memblock from doing this.
>> 
>> So direct memory mapping page tables setup is the case.
>init_mem_mapping()
>> is called before SRAT is parsed. To prevent page tables being
>allocated
>> within hotpluggable memory, we will use bottom-up direction to
>allocate
>> page tables from the end of kernel image to the higher memory.
>> 
>> ...
>>
>> +		kernel_end = __pa_symbol(_end);
>
>__pa_symbol() is implemented only on mips and x86.
>
>I stole the mips implementation like this:
>
>--- a/mm/memblock.c~a
>+++ a/mm/memblock.c
>@@ -187,8 +187,11 @@ phys_addr_t __init_memblock memblock_fin
> 	/* avoid allocating the first page */
> 	start = max_t(phys_addr_t, start, PAGE_SIZE);
> 	end = max(start, end);
>+#ifdef CONFIG_X86
> 	kernel_end = __pa_symbol(_end);
>-
>+#else
>+	kernel_end = __pa(RELOC_HIDE((unsigned long)(_end), 0));
>+#endif
> 	/*
> 	 * try bottom-up allocation only when bottom-up mode
> 	 * is set and @end is above the kernel image.
>
>just so I can get a -mm release out the door.

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
--
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/