[PATCH] x86: fix booting non-NUMA system with NUMA config

[PATCH] x86: fix booting non-NUMA system with NUMA config

[Dave Hansen]

[-- Attachment #1: Type: text/plain, Size: 1100 bytes --]

On Fri, 2005-03-11 at 19:25 +0000, Hugh Dickins wrote:
> This used to work fine, but around the time your abstract discontigmem
> patches went into -mm, the resulting kernel failed to boot - blank
> screen after grub for a few seconds, until it reboots again.  And now
> your patches have just gone into mainline, that resulting kernel fails
> to boot.  I've not done a binary search to identify any one of your
> patches as the culprit, but you are my Number One suspect ;)

Hugh, you caught me.  There is, indeed, a bug booting with
CONFIG_NUMA=y, CONFIG_X86_GENERICARCH=y, and booting on a non-NUMA
system.  While not the most common configuration, it should surely be
supported.

memmap_init_zone() is the first user to do pfn_to_nid(), which relies on
physnode_map[] to be done properly.  memory_present() was supposed to do
that, but never got called for the flat configuration, so pfn_to_nid()
was returning -1 on valid pages.

Andrew, please apply and forward the attached patch on to Linus.  It
affects code currently in -bk.

Test compiled and booted on 4-way non-NUMA x86 system.

-- Dave

[-- Attachment #2: memory_present_for_flat.patch --]
[-- Type: text/x-patch, Size: 609 bytes --]



---

 memhotplug-dave/arch/i386/mm/discontig.c |    1 +
 1 files changed, 1 insertion(+)

diff -puN arch/i386/mm/discontig.c~memory_present_for_flat arch/i386/mm/discontig.c
--- memhotplug/arch/i386/mm/discontig.c~memory_present_for_flat	2005-03-11 12:29:45.000000000 -0800
+++ memhotplug-dave/arch/i386/mm/discontig.c	2005-03-11 12:30:04.000000000 -0800
@@ -121,6 +121,7 @@ int __init get_memcfg_numa_flat(void)
 	find_max_pfn();
 	node_start_pfn[0] = 0;
 	node_end_pfn[0] = max_pfn;
+	memory_present(0, 0, max_pfn);
 
         /* Indicate there is one node available. */
 	nodes_clear(node_online_map);
_

Re: [PATCH] x86: fix booting non-NUMA system with NUMA config

[Hugh Dickins]

On Fri, 11 Mar 2005, Dave Hansen wrote:
> 
> Hugh, you caught me.  There is, indeed, a bug booting with
> CONFIG_NUMA=y, CONFIG_X86_GENERICARCH=y, and booting on a non-NUMA
> system.  While not the most common configuration, it should surely be
> supported.

Lovely, Dave, thanks a lot, I confirm your patch works for me.
Now I can impress the neighbours again with my little "NUMA" system.

Hugh
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