Re: [PATCH -v3 0/7] x86: Use BRK to pre mapping page table to make xen happy

[Yinghai Lu <yinghai@kernel.org>]

[-- Attachment #1: Type: text/plain, Size: 1855 bytes --]

On Wed, Nov 7, 2012 at 5:40 PM, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
>
> I ran in a problem with launching an 8GB guest. When launching a 4GB it worked
> fine, but with 8GB I get:
>
> .000000] init_memory_mapping: [mem 0x1f4000000-0x1f47fffff]
> [    0.000000]  [mem 0x1f4000000-0x1f47fffff] page 4k
> [    0.000000] memblock_reserve: [0x000001f311c000-0x000001f311d000] alloc_low_pages+0x103/0x130
> [    0.000000] memblock_reserve: [0x000001f311b000-0x000001f311c000] alloc_low_pages+0x103/0x130
> [    0.000000] memblock_reserve: [0x000001f311a000-0x000001f311b000] alloc_low_pages+0x103/0x130
> [    0.000000] memblock_reserve: [0x000001f3119000-0x000001f311a000] alloc_low_pages+0x103/0x130
> [    0.000000] Kernel panic - not syncing: initrd too large to handle, disabling initrd (348401664 needed, 524288 available)
> [    0.000000]
> [    0.000000] Pid: 0, comm: swapper Not tainted 3.7.0-rc4upstream-00042-g1b66ccf #1
> [    0.000000] Call Trace:
> [    0.000000]  [<ffffffff81633a5c>] panic+0xbf/0x1df
> [    0.000000]  [<ffffffff81ac00e1>] setup_arch+0x728/0xb29
> [    0.000000]  [<ffffffff81633c48>] ? printk+0x48/0x4a
> [    0.000000]  [<ffffffff81aba897>] start_kernel+0x90/0x39e
> [    0.000000]  [<ffffffff81aba356>] x86_64_start_reservations+0x131/0x136
> [    0.000000]  [<ffffffff81abca38>] xen_start_kernel+0x546/0x548
>

xen memmap

[    0.000000] Xen: [mem 0x0000000000000000-0x000000000009ffff] usable
[    0.000000] Xen: [mem 0x00000000000a0000-0x00000000000fffff] reserved
[    0.000000] Xen: [mem 0x0000000000100000-0x00000001f47fffff] usable

there is no hole under 4G, trigger the bug about max_low_pfn_mapped updating in
add_pfn_range_mapped().

please check attached patch, that should fix the problem.

then I will fold it into corresponding commit that instroduce
add_pfn_range_mapped().

Thanks

Yinghai

[-- Attachment #2: fix_max_low_pfn_mapped.patch --]
[-- Type: application/octet-stream, Size: 692 bytes --]

---
 arch/x86/mm/init.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/mm/init.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/init.c
+++ linux-2.6/arch/x86/mm/init.c
@@ -305,8 +305,9 @@ static void add_pfn_range_mapped(unsigne
 
 	max_pfn_mapped = max(max_pfn_mapped, end_pfn);
 
-	if (end_pfn <= (1UL << (32 - PAGE_SHIFT)))
-		max_low_pfn_mapped = max(max_low_pfn_mapped, end_pfn);
+	if (start_pfn < (1UL<<(32-PAGE_SHIFT)))
+		max_low_pfn_mapped = max(max_low_pfn_mapped,
+					 min(end_pfn, 1UL<<(32-PAGE_SHIFT)));
 }
 
 bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn)