Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Qian Cai]

On Tue, 2019-10-15 at 20:51 +0530, Anshuman Khandual wrote:
> 
> On 10/15/2019 08:11 PM, Qian Cai wrote:
> > The x86 will crash with linux-next during boot due to this series (v5) with the
> > config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
> > it.
> > 
> > https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
> > 
> > [ÂÂÂ33.862600][ÂÂÂÂT1] page:ffffea0009000000 is uninitialized and poisoned
> > [ÂÂÂ33.862608][ÂÂÂÂT1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
> > ffffff871140][ÂÂÂÂT1]ÂÂ? _raw_spin_unlock_irq+0x27/0x40
> > [ÂÂÂ33.871140][ÂÂÂÂT1]ÂÂ? rest_init+0x307/0x307
> > [ÂÂÂ33.871140][ÂÂÂÂT1]ÂÂkernel_init+0x11/0x139
> > [ÂÂÂ33.871140][ÂÂÂÂT1]ÂÂ? rest_init+0x307/0x307
> > [ÂÂÂ33.871140][ÂÂÂÂT1]ÂÂret_from_fork+0x27/0x50
> > [ÂÂÂ33.871140][ÂÂÂÂT1] Modules linked in:
> > [ÂÂÂ33.871140][ÂÂÂÂT1] ---[ end trace e99d392b0f7befbd ]---
> > [ÂÂÂ33.871140][ÂÂÂÂT1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490
> 
> Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
> with the config above, it does. Just wondering if it is possible that these
> pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?

Yes, this patch works fine.

diff --git a/init/main.c b/init/main.c
index 676d8020dd29..591be8f9e8e0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1177,7 +1177,6 @@ static noinline void __init kernel_init_freeable(void)
ÂÂÂÂÂÂÂÂworkqueue_init();
Â
ÂÂÂÂÂÂÂÂinit_mm_internals();
-ÂÂÂÂÂÂÂdebug_vm_pgtable();
Â
ÂÂÂÂÂÂÂÂdo_pre_smp_initcalls();
ÂÂÂÂÂÂÂÂlockup_detector_init();
@@ -1186,6 +1185,8 @@ static noinline void __init kernel_init_freeable(void)
ÂÂÂÂÂÂÂÂsched_init_smp();
Â
ÂÂÂÂÂÂÂÂpage_alloc_init_late();
+ÂÂÂÂÂÂÂdebug_vm_pgtable();
+
ÂÂÂÂÂÂÂÂ/* Initialize page ext after all struct pages are initialized. */
ÂÂÂÂÂÂÂÂpage_ext_init();

> 
> [   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
> [   13.898549][    T1] ------------[ cut here ]------------
> [   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
> [   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> [   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #