Re: [tip:core/memblock] x86-64: Only set max_pfn_mapped to 512 MiB if we enter via head_64.S

Yinghai Lu
2010-10-14T07:05:18Z

On 10/13/2010 11:37 PM, Ingo Molnar wrote:
>
> * Yinghai Lu <yinghai@kernel.org> wrote:
>
>> On 10/13/2010 10:57 PM, Ingo Molnar wrote:
>>>
>>> * tip-bot for Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>>>
>>>> Commit-ID: 859ee4f57fb4e91de8439496f62eb996f4a28ca8
>>>> Gitweb: http://git.kernel.org/tip/859ee4f57fb4e91de8439496f62eb996f4a28ca8
>>>> Author: Jeremy Fitzhardinge <jeremy@goop.org>
>>>> AuthorDate: Wed, 13 Oct 2010 16:34:15 -0700
>>>> Committer: H. Peter Anvin <hpa@linux.intel.com>
>>>> CommitDate: Wed, 13 Oct 2010 17:09:59 -0700
>>>>
>>>> x86-64: Only set max_pfn_mapped to 512 MiB if we enter via head_64.S
>>>>
>>>> head_64.S maps up to 512 MiB, but that is not necessarity true for
>>>> other entry paths, such as Xen.
>>>

please fold following patch into 859ee4f57fb4e91de8439496f62eb996f4a28ca8

Thanks

Yinghai

[PATCH] x86_64: Set max_pfn_mapped in x86_64_start_kernel

Ingo found:
[ 0.000000] init_memory_mapping: 0000000000000000-000000003fff0000
[ 0.000000] 0000000000 - 003fe00000 page 2M
[ 0.000000] 003fe00000 - 003fff0000 page 4k
[ 0.000000] Kernel panic - not syncing: Cannot find space for the kernel page tables
[ 0.000000] Pid: 0, comm: swapper Not tainted 2.6.36-rc7-tip+ #49192
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffff8156c73f>] panic+0x8c/0x192
[ 0.000000] [<ffffffff8156c881>] ? printk+0x3c/0x3e
[ 0.000000] [<ffffffff8154ec40>] init_memory_mapping+0x372/0x506
[ 0.000000] [<ffffffff819053ed>] ? memblock_x86_reserve_range+0x7c/0x83
[ 0.000000] [<ffffffff818f2f3d>] setup_arch+0x5a3/0xa68
[ 0.000000] [<ffffffff8156c881>] ? printk+0x3c/0x3e
[ 0.000000] [<ffffffff81061135>] ? clockevents_register_notifier+0x3e/0x4a
[ 0.000000] [<ffffffff818ef9e1>] start_kernel+0x83/0x36e
[ 0.000000] [<ffffffff818ef2a8>] x86_64_start_reservations+0xb8/0xbc
[ 0.000000] [<ffffffff818ef393>] x86_64_start_kernel+0xe7/0xee

caused by:
| 859ee4f: x86-64: Only set max_pfn_mapped to 512 MiB if we enter via head_64.S

it turns out max_pfn_mapped is in .bss section.

So We need to set that after bss get cleared.

that is safe because xen don't call x86_64_start_kernel()

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
arch/x86/kernel/head64.c | 2 ++
arch/x86/kernel/head_64.S | 2 --
2 files changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/kernel/head64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head64.c
+++ linux-2.6/arch/x86/kernel/head64.c
@@ -80,6 +80,8 @@ void __init x86_64_start_kernel(char * r
/* Cleanup the over mapped high alias */
cleanup_highmap();

+ max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT;
+
for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) {
#ifdef CONFIG_EARLY_PRINTK
set_intr_gate(i, &early_idt_handlers[i]);
Index: linux-2.6/arch/x86/kernel/head_64.S
===================================================================
--- linux-2.6.orig/arch/x86/kernel/head_64.S
+++ linux-2.6/arch/x86/kernel/head_64.S
@@ -141,8 +141,6 @@ ident_complete:
addq %rbp, trampoline_level4_pgt + (511*8)(%rip)
#endif

- movq $KERNEL_IMAGE_SIZE / PAGE_SIZE, max_pfn_mapped(%rip)
-
/* Due to ENTRY(), sometimes the empty space gets filled with
* zeros. Better take a jmp than relying on empty space being
* filled with 0x90 (nop)