linux-kernel - Re: [PATCH Bug fix] acpi, movablemem_map: node0 should always be unhotpluggable when using SRAT.

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Date:	Wed, 30 Jan 2013 07:55:11 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Tang Chen <tangchen@...fujitsu.com>, akpm@...ux-foundation.org,
	jiang.liu@...wei.com, wujianguo@...wei.com, wency@...fujitsu.com,
	laijs@...fujitsu.com, linfeng@...fujitsu.com, yinghai@...nel.org,
	isimatu.yasuaki@...fujitsu.com, rob@...dley.net,
	kosaki.motohiro@...fujitsu.com, minchan.kim@...il.com,
	mgorman@...e.de, rientjes@...gle.com, guz.fnst@...fujitsu.com,
	rusty@...tcorp.com.au, lliubbo@...il.com, jaegeuk.hanse@...il.com,
	tony.luck@...el.com, glommer@...allels.com
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH Bug fix] acpi, movablemem_map: node0 should always be unhotpluggable when using SRAT.

It is not node 0, it is whatever node the kernel resides in.

Tang Chen <tangchen@...fujitsu.com> wrote:

>When using movablemem_map=acpi, always set node0 as unhotpluggable,
>otherwise
>if all the memory is hotpluggable, the kernel will fail to boot.
>
>When using movablemem_map=nn[KMG]@ss[KMG], we don't stop users
>specifying
>node0 as hotpluggable, and ignore all the info in SRAT, so that this
>option
>can be used as a workaround of firmware bugs.
>
>Reported-by: H. Peter Anvin <hpa@...or.com>
>Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
>---
> Documentation/kernel-parameters.txt |    6 ++++++
> arch/x86/mm/srat.c                  |   10 ++++++++--
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
>diff --git a/Documentation/kernel-parameters.txt
>b/Documentation/kernel-parameters.txt
>index 7d1b6fc..81b6f15 100644
>--- a/Documentation/kernel-parameters.txt
>+++ b/Documentation/kernel-parameters.txt
>@@ -1645,6 +1645,8 @@ bytes respectively. Such letter suffixes can also
>be entirely omitted.
> 			in flags from SRAT from ACPI BIOS to determine which
> 			memory devices could be hotplugged. The corresponding
> 			memory ranges will be set as ZONE_MOVABLE.
>+			NOTE: node0 should always be unhotpluggable, otherwise
>+			      the kernel will fail to boot.
> 
> 	movablemem_map=nn[KMG]@ss[KMG]
> 			[KNL,X86,IA-64,PPC] This parameter is similar to
>@@ -1666,6 +1668,10 @@ bytes respectively. Such letter suffixes can
>also be entirely omitted.
> 			satisfied. So the administrator should be careful that
> 			the amount of movablemem_map areas are not too large.
> 			Otherwise kernel won't have enough memory to start.
>+			NOTE: We don't stop users specifying node0 as
>+			      hotpluggable, and ingore all the info in SRAT so
>+			      that this option can be used as a workaround of
>+			      firmware bugs.
> 
> 	MTD_Partition=	[MTD]
> 			Format: <name>,<region-number>,<size>,<offset>
>diff --git a/arch/x86/mm/srat.c b/arch/x86/mm/srat.c
>index b20b5b7..a85d2b7 100644
>--- a/arch/x86/mm/srat.c
>+++ b/arch/x86/mm/srat.c
>@@ -161,9 +161,13 @@ handle_movablemem(int node, u64 start, u64 end,
>u32 hotpluggable)
> 	 *
>	 * Using movablemem_map, we can prevent memblock from allocating
>memory
> 	 * on ZONE_MOVABLE at boot time.
>+	 *
>+	 * NOTE: node0 shoule always be unhotpluggable, otherwise, if all the
>+	 *       memory is hotpluggable, there will be no memory kernel can
>use.
> 	 */
> 	if (hotpluggable && movablemem_map.acpi) {
>-		insert_movablemem_map(start_pfn, end_pfn);
>+		if (node != 0)
>+			insert_movablemem_map(start_pfn, end_pfn);
> 		goto out;
> 	}
> 
>@@ -178,7 +182,9 @@ handle_movablemem(int node, u64 start, u64 end, u32
>hotpluggable)
>	 * Using movablemem_map, we can prevent memblock from allocating
>memory
> 	 * on ZONE_MOVABLE at boot time.
> 	 *
>-	 * NOTE: In this case, SRAT info will be ingored.
>+	 * NOTE: We don't stop users specifying node0 as hotpluggable, and
>+	 *       ignore all the info in SRAT, so that this option can be used
>+	 *       as a workaround of firmware bugs.
> 	 */
> 	overlap = movablemem_map_overlap(start_pfn, end_pfn);
> 	if (overlap >= 0) {

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