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Re: [Xen-devel] Linux 4.15-rc6 + xen-unstable: BUG: unable to handle kernel NULL pointer dereference at (null), [ 0.000000] IP: zero_resv_unavail+0x8e/0xe1



On 09/01/18 16:29, Sander Eikelenboom wrote:
> Since it's already rc7:
> "Give me a subtle ping, Vasili. One subtle ping only, please."

I like that film :-)

Pavel, can you please comment? Do you have an idea how to repair the
issue or should we revert your patch in 4.15?


Juergen

> 
> On 04/01/18 21:02, Sander Eikelenboom wrote:
>> On 04/01/18 12:44, Juergen Gross wrote:
>>> On 04/01/18 11:17, Sander Eikelenboom wrote:
>>>> Hi Boris / Juergen,
>>>>
>>>> First of all best wishes for a quite turbulent starting new year.
>>>>
>>>> Now the holidays are over I finally gotten to test a linux 4.15-rc6 kernel
>>>> and experienced a crash in early dom0 boot on my system (AMD phenom x6).
>>>>
>>>> I tested some earlier linux 4.15 rc's but experienced crashes then as 
>>>> well, 
>>>> but didn't have time to setup serial console to send them in 
>>>> (and waited to see if the issue Boris fixed with AMD PCI 64bit bar's could 
>>>> be it). 
>>>>
>>>> But since that patch went in before 4.15 rc6, that doesn't seem to be the 
>>>> issue. 
>>>> So it could be that the culprit went in pretty earlier in the 4.15 cycle.
>>>>
>>>> The 4.15-rc6 kernel boots fine on bare metal, as does a 4.14.6 kernel on 
>>>> xen-unstable.
>>>>
>>>> Hopefully you have a pointer to what is wrong, if not i can try to do a 
>>>> bisect.
>>>
>>> A bisect would be very welcome.
>>
>> Hi Juergen / Boris / Pavel,
>>
>> Bisection result is:
>>
>> a4a3ede2132ae0863e2d43e06f9b5697c51a7a3b is the first bad commit
>> commit a4a3ede2132ae0863e2d43e06f9b5697c51a7a3b
>> Author: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
>> Date:   Wed Nov 15 17:36:31 2017 -0800
>>
>>     mm: zero reserved and unavailable struct pages
>>     
>>     Some memory is reserved but unavailable: not present in memblock.memory
>>     (because not backed by physical pages), but present in memblock.reserved.
>>     Such memory has backing struct pages, but they are not initialized by
>>     going through __init_single_page().
>>     
>>     In some cases these struct pages are accessed even if they do not
>>     contain any data.  One example is page_to_pfn() might access page->flags
>>     if this is where section information is stored (CONFIG_SPARSEMEM,
>>     SECTION_IN_PAGE_FLAGS).
>>     
>>     One example of such memory: trim_low_memory_range() unconditionally
>>     reserves from pfn 0, but e820__memblock_setup() might provide the
>>     exiting memory from pfn 1 (i.e.  KVM).
>>     
>>     Since struct pages are zeroed in __init_single_page(), and not during
>>     allocation time, we must zero such struct pages explicitly.
>>     
>>     The patch involves adding a new memblock iterator:
>>             for_each_resv_unavail_range(i, p_start, p_end)
>>     
>>     Which iterates through reserved && !memory lists, and we zero struct 
>> pages
>>     explicitly by calling mm_zero_struct_page().
>>     
>>     ===
>>     
>>     Here is more detailed example of problem that this patch is addressing:
>>     
>>     Run tested on qemu with the following arguments:
>>     
>>             -enable-kvm -cpu kvm64 -m 512 -smp 2
>>     
>>     This patch reports that there are 98 unavailable pages.
>>     
>>     They are: pfn 0 and pfns in range [159, 255].
>>     
>>     Note, trim_low_memory_range() reserves only pfns in range [0, 15], it 
>> does
>>     not reserve [159, 255] ones.
>>     
>>     e820__memblock_setup() reports linux that the following physical ranges 
>> are
>>     available:
>>         [1 , 158]
>>     [256, 130783]
>>     
>>     Notice, that exactly unavailable pfns are missing!
>>     
>>     Now, lets check what we have in zone 0: [1, 131039]
>>     
>>     pfn 0, is not part of the zone, but pfns [1, 158], are.
>>     
>>     However, the bigger problem we have if we do not initialize these struct
>>     pages is with memory hotplug.  Because, that path operates at 2M
>>     boundaries (section_nr).  And checks if 2M range of pages is hot
>>     removable.  It starts with first pfn from zone, rounds it down to 2M
>>     boundary (sturct pages are allocated at 2M boundaries when vmemmap is
>>     created), and checks if that section is hot removable.  In this case
>>     start with pfn 1 and convert it down to pfn 0.  Later pfn is converted
>>     to struct page, and some fields are checked.  Now, if we do not zero
>>     struct pages, we get unpredictable results.
>>     
>>     In fact when CONFIG_VM_DEBUG is enabled, and we explicitly set all
>>     vmemmap memory to ones, the following panic is observed with kernel test
>>     without this patch applied:
>>     
>>       BUG: unable to handle kernel NULL pointer dereference at          
>> (null)
>>       IP: is_pageblock_removable_nolock+0x35/0x90
>>       PGD 0 P4D 0
>>       Oops: 0000 [#1] PREEMPT
>>       ...
>>       task: ffff88001f4e2900 task.stack: ffffc90000314000
>>       RIP: 0010:is_pageblock_removable_nolock+0x35/0x90
>>       Call Trace:
>>        ? is_mem_section_removable+0x5a/0xd0
>>        show_mem_removable+0x6b/0xa0
>>        dev_attr_show+0x1b/0x50
>>        sysfs_kf_seq_show+0xa1/0x100
>>        kernfs_seq_show+0x22/0x30
>>        seq_read+0x1ac/0x3a0
>>        kernfs_fop_read+0x36/0x190
>>        ? security_file_permission+0x90/0xb0
>>        __vfs_read+0x16/0x30
>>        vfs_read+0x81/0x130
>>        SyS_read+0x44/0xa0
>>        entry_SYSCALL_64_fastpath+0x1f/0xbd
>>     
>>     Link: 
>> http://lkml.kernel.org/r/20171013173214.27300-7-pasha.tatashin@xxxxxxxxxx
>>     Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
>>     Reviewed-by: Steven Sistare <steven.sistare@xxxxxxxxxx>
>>     Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
>>     Reviewed-by: Bob Picco <bob.picco@xxxxxxxxxx>
>>     Tested-by: Bob Picco <bob.picco@xxxxxxxxxx>
>>     Acked-by: Michal Hocko <mhocko@xxxxxxxx>
>>     Cc: Alexander Potapenko <glider@xxxxxxxxxx>
>>     Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
>>     Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>>     Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
>>     Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>>     Cc: David S. Miller <davem@xxxxxxxxxxxxx>
>>     Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
>>     Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
>>     Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
>>     Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>>     Cc: Mark Rutland <mark.rutland@xxxxxxx>
>>     Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
>>     Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
>>     Cc: Michal Hocko <mhocko@xxxxxxxxxx>
>>     Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
>>     Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>>     Cc: Will Deacon <will.deacon@xxxxxxx>
>>     Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>     Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>>
>> :040000 040000 b0422cb4f5ef60f5bc7f0686d135c869680c603d 
>> 51ef20afe641afceaf5530b83b4f1b9a51563939 M   include
>> :040000 040000 55be7a5dd879578dc3f88bec059bcc392e3f1a1c 
>> b4c9f81df05629bb034b6d0bdc0454579f2986fe M   mm
>>
>>
>> --
>> Sander
>>
>>>
>>> Juergen
>>>
>>>>
>>>> --
>>>> Sander
>>>>
>>>> Attached: .config and full serial log
>>>>
>>>>  0.000000] ACPI: Early table checksum verification disabled
>>>> [    0.000000] ACPI: RSDP 0x00000000000FB100 000014 (v00 ACPIAM)
>>>> [    0.000000] ACPI: RSDT 0x00000000C7F90000 000048 (v01 MSI    OEMSLIC  
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: FACP 0x00000000C7F90200 000084 (v01 7640MS A7640100 
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: DSDT 0x00000000C7F905E0 009427 (v01 A7640  A7640100 
>>>> 00000100 INTL 20051117)
>>>> [    0.000000] ACPI: FACS 0x00000000C7F9E000 000040
>>>> [    0.000000] ACPI: APIC 0x00000000C7F90390 000088 (v01 7640MS A7640100 
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: MCFG 0x00000000C7F90420 00003C (v01 7640MS OEMMCFG  
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: SLIC 0x00000000C7F90460 000176 (v01 MSI    OEMSLIC  
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: OEMB 0x00000000C7F9E040 000072 (v01 7640MS A7640100 
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: SRAT 0x00000000C7F9A5E0 000108 (v03 AMD    FAM_F_10 
>>>> 00000002 AMD  00000001)
>>>> [    0.000000] ACPI: HPET 0x00000000C7F9A6F0 000038 (v01 7640MS OEMHPET  
>>>> 20100913 MSFT 00000097)
>>>> [    0.000000] ACPI: IVRS 0x00000000C7F9A730 000110 (v01 AMD    RD890S   
>>>> 00202031 AMD  00000000)
>>>> [    0.000000] ACPI: SSDT 0x00000000C7F9A840 000DA4 (v01 A M I  POWERNOW 
>>>> 00000001 AMD  00000001)
>>>> [    0.000000] ACPI: Local APIC address 0xfee00000
>>>> [    0.000000] Setting APIC routing to Xen PV.
>>>> [    0.000000] NUMA turned off
>>>> [    0.000000] Faking a node at [mem 0x0000000000000000-0x000000007fffffff]
>>>> [    0.000000] NODE_DATA(0) allocated [mem 0x7fc15000-0x7fc1efff]
>>>> [    0.000000] tsc: Fast TSC calibration using PIT
>>>> [    0.000000] Zone ranges:
>>>> [    0.000000]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
>>>> [    0.000000]   DMA32    [mem 0x0000000001000000-0x000000007fffffff]
>>>> [    0.000000]   Normal   empty
>>>> [    0.000000] Movable zone start for each node
>>>> [    0.000000] Early memory node ranges
>>>> [    0.000000]   node   0: [mem 0x0000000000001000-0x0000000000095fff]
>>>> [    0.000000]   node   0: [mem 0x0000000000100000-0x000000007fffffff]
>>>> [    0.000000] Initmem setup node 0 [mem 
>>>> 0x0000000000001000-0x000000007fffffff]
>>>> [    0.000000] On node 0 totalpages: 524181
>>>> [    0.000000]   DMA zone: 64 pages used for memmap
>>>> [    0.000000]   DMA zone: 21 pages reserved
>>>> [    0.000000]   DMA zone: 3989 pages, LIFO batch:0
>>>> [    0.000000]   DMA32 zone: 8128 pages used for memmap
>>>> [    0.000000]   DMA32 zone: 520192 pages, LIFO batch:31
>>>> [    0.000000] BUG: unable to handle kernel NULL pointer dereference at    
>>>>        (null)
>>>> [    0.000000] IP: zero_resv_unavail+0x8e/0xe1
>>>> [    0.000000] PGD 0 P4D 0 
>>>> [    0.000000] Oops: 0002 [#1] SMP
>>>> [    0.000000] Modules linked in:
>>>> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 
>>>> 4.15.0-rc6-20180104-linus-doflr+ #1
>>>> [    0.000000] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS 
>>>> V1.8B1 09/13/2010
>>>> [    0.000000] RIP: e030:zero_resv_unavail+0x8e/0xe1
>>>> [    0.000000] RSP: e02b:ffffffff82803d68 EFLAGS: 00010006
>>>> [    0.000000] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 
>>>> 0000000000000010
>>>> [    0.000000] RDX: 000000000007ffff RSI: 0000000000000100 RDI: 
>>>> ffffea0002000000
>>>> [    0.000000] RBP: ffffffff82803d70 R08: ffffea0002000000 R09: 
>>>> 0000000000000002
>>>> [    0.000000] R10: 0000000000000002 R11: 0000000000000003 R12: 
>>>> ffffea0000000000
>>>> [    0.000000] R13: 0000000000000000 R14: ffffffff82803f20 R15: 
>>>> 0000000000000000
>>>> [    0.000000] FS:  0000000000000000(0000) GS:ffffffff82e16000(0000) 
>>>> knlGS:0000000000000000
>>>> [    0.000000] CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [    0.000000] CR2: 0000000000000000 CR3: 0000000002823000 CR4: 
>>>> 0000000000000660
>>>> [    0.000000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
>>>> 0000000000000000
>>>> [    0.000000] DR3: 0000000000000000 DR6: 0000000000000000 DR7: 
>>>> 0000000000000000
>>>> [    0.000000] Call Trace:
>>>> [    0.000000]  ? free_area_init_nodes+0x690/0x69f
>>>> [    0.000000]  ? zone_sizes_init+0x4b/0x50
>>>> [    0.000000]  ? xen_pagetable_init+0x13/0x43f
>>>> [    0.000000]  ? memblock_find_dma_reserve+0x141/0x15b
>>>> [    0.000000]  ? memblock_find_dma_reserve+0x150/0x15b
>>>> [    0.000000]  ? numa_init+0x43c/0x453
>>>> [    0.000000]  ? setup_arch+0x7a0/0x87f
>>>> [    0.000000]  ? start_kernel+0x58/0x3a8
>>>> [    0.000000]  ? iommu_shutdown_noop+0x10/0x10
>>>> [    0.000000]  ? xen_start_kernel+0x528/0x534
>>>> [    0.000000] Code: da 49 c1 e0 06 4d 01 e0 48 8b 44 24 08 48 8d 0c 1a 48 
>>>> 05 ff 0f 00 00 48 c1 e8 0c 48 39 c8 76 16 4c 89 c7 b9 10 00 00 00 44 89 e8 
>>>> <f3> ab 48 ff c3 49 83 c0 40 eb d2 6a 00 55 31 d2 49 c7 c0 90 78 
>>>> [    0.000000] RIP: zero_resv_unavail+0x8e/0xe1 RSP: ffffffff82803d68
>>>> [    0.000000] CR2: 0000000000000000
>>>> [    0.000000] ---[ end trace b788f32e38f6de39 ]---
>>>> [    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
>>>> (XEN) [2018-01-04 09:52:49.218] Hardware Dom0 crashed: rebooting machine 
>>>> in 5 seconds.
>>>>
>>>
>>
> 
> 


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