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From: Wu Fengguang <fengguang.wu@intel.com>
To: "Zheng, Shaohui" <shaohui.zheng@intel.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"ak@linux.intel.com" <ak@linux.intel.com>,
	"y-goto@jp.fujitsu.com" <y-goto@jp.fujitsu.com>,
	Dave Hansen <haveblue@us.ibm.com>,
	"x86@kernel.org" <x86@kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1)
Date: Mon, 11 Jan 2010 20:43:03 +0800	[thread overview]
Message-ID: <20100111124303.GA21408@localhost> (raw)
In-Reply-To: <DA586906BA1FFC4384FCFD6429ECE86031560FC1@shzsmsx502.ccr.corp.intel.com>

> > +	/* if add to low memory, update max_low_pfn */
> > +	if (unlikely(start_pfn < limit_low_pfn)) {
> > +		if (end_pfn <= limit_low_pfn)
> > +			max_low_pfn = end_pfn;
> > +		else
> > +			max_low_pfn = limit_low_pfn;
> 
> X86_64 actually always set max_low_pfn=max_pfn, in setup_arch():
> [Zheng, Shaohui] there should be some misunderstanding, I read the
> code carefully, if the total memory is under 4G, it always
> max_low_pfn=max_pfn. If the total memory is larger than 4G,
> max_low_pfn means the end of low ram. It set

> max_low_pfn = e820_end_of_low_ram_pfn();.

The above line is very misleading.. In setup_arch(), it will be
overrode by the following block.

>  899 #ifdef CONFIG_X86_64
>  900         if (max_pfn > max_low_pfn) {
>  901                 max_pfn_mapped = init_memory_mapping(1UL<<32,
>  902                                                      max_pfn<<PAGE_SHIFT);
>  903                 /* can we preseve max_low_pfn ?*/
>  904                 max_low_pfn = max_pfn;
>  905         }
>  906 #endif
 
Thanks,
Fengguang

WARNING: multiple messages have this Message-ID (diff)
From: Wu Fengguang <fengguang.wu@intel.com>
To: "Zheng, Shaohui" <shaohui.zheng@intel.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"ak@linux.intel.com" <ak@linux.intel.com>,
	"y-goto@jp.fujitsu.com" <y-goto@jp.fujitsu.com>,
	Dave Hansen <haveblue@us.ibm.com>,
	"x86@kernel.org" <x86@kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1)
Date: Mon, 11 Jan 2010 20:43:03 +0800	[thread overview]
Message-ID: <20100111124303.GA21408@localhost> (raw)
In-Reply-To: <DA586906BA1FFC4384FCFD6429ECE86031560FC1@shzsmsx502.ccr.corp.intel.com>

> > +	/* if add to low memory, update max_low_pfn */
> > +	if (unlikely(start_pfn < limit_low_pfn)) {
> > +		if (end_pfn <= limit_low_pfn)
> > +			max_low_pfn = end_pfn;
> > +		else
> > +			max_low_pfn = limit_low_pfn;
> 
> X86_64 actually always set max_low_pfn=max_pfn, in setup_arch():
> [Zheng, Shaohui] there should be some misunderstanding, I read the
> code carefully, if the total memory is under 4G, it always
> max_low_pfn=max_pfn. If the total memory is larger than 4G,
> max_low_pfn means the end of low ram. It set

> max_low_pfn = e820_end_of_low_ram_pfn();.

The above line is very misleading.. In setup_arch(), it will be
overrode by the following block.

>  899 #ifdef CONFIG_X86_64
>  900         if (max_pfn > max_low_pfn) {
>  901                 max_pfn_mapped = init_memory_mapping(1UL<<32,
>  902                                                      max_pfn<<PAGE_SHIFT);
>  903                 /* can we preseve max_low_pfn ?*/
>  904                 max_low_pfn = max_pfn;
>  905         }
>  906 #endif
 
Thanks,
Fengguang

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  reply	other threads:[~2010-01-11 12:43 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-01-08  3:32 [PATCH - resend] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel(v1) Zheng, Shaohui
2010-01-08  5:02 ` H. Peter Anvin
2010-01-08  5:02   ` H. Peter Anvin
2010-01-08  5:18   ` Zheng, Shaohui
2010-01-08  5:18     ` Zheng, Shaohui
2010-01-08 19:47   ` Andi Kleen
2010-01-08 19:47     ` Andi Kleen
2010-01-12  0:58     ` KAMEZAWA Hiroyuki
2010-01-12  0:58       ` KAMEZAWA Hiroyuki
2010-01-08 12:48 ` Wu Fengguang
2010-01-08 12:48   ` Wu Fengguang
2010-01-11  2:20   ` Zheng, Shaohui
2010-01-11  2:20     ` Zheng, Shaohui
2010-01-11 12:43     ` Wu Fengguang [this message]
2010-01-11 12:43       ` Wu Fengguang
2010-01-12  0:30       ` KAMEZAWA Hiroyuki
2010-01-12  0:30         ` KAMEZAWA Hiroyuki
2010-01-12  1:38         ` Andi Kleen
2010-01-12  1:38           ` Andi Kleen
2010-01-12  1:39           ` KAMEZAWA Hiroyuki
2010-01-12  1:39             ` KAMEZAWA Hiroyuki
2010-01-12  1:50             ` KAMEZAWA Hiroyuki
2010-01-12  1:50               ` KAMEZAWA Hiroyuki
2010-01-12  2:45               ` Wu Fengguang
2010-01-12  2:45                 ` Wu Fengguang
2010-01-12  2:33         ` Wu Fengguang
2010-01-12  2:33           ` Wu Fengguang
2010-01-12  2:39           ` KAMEZAWA Hiroyuki
2010-01-12  2:39             ` KAMEZAWA Hiroyuki
2010-01-12 13:35             ` Wu Fengguang
2010-01-12 13:35               ` Wu Fengguang
2010-01-12 23:01               ` Yinghai Lu
2010-01-12 23:01                 ` Yinghai Lu
2010-01-13  2:29                 ` Wu Fengguang
2010-01-13  2:29                   ` Wu Fengguang
2010-01-12  5:45         ` Zheng, Shaohui
2010-01-12  5:45           ` Zheng, Shaohui
2010-01-12  5:51       ` Zheng, Shaohui
2010-01-12  5:51         ` Zheng, Shaohui

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