Re: [Xen-devel] [xen-unstable test] 127070: regressions - FAIL

[Juergen Gross <jgross@xxxxxxxx>]

On 03/09/18 14:44, Jan Beulich wrote:
>>>> On 01.09.18 at 23:43, <osstest-admin@xxxxxxxxxxxxxx> wrote:
>> flight 127070 xen-unstable real [real]
>> http://logs.test-lab.xenproject.org/osstest/logs/127070/ 
>>
>> Regressions :-(
>>
>> Tests which did not succeed and are blocking,
>> including tests which could not be run:
>>  test-amd64-i386-xl-shadow   20 guest-start/debian.repeat fail REGR. vs. 
>> 126854
> 
> I wonder if this
> 
> [   30.017142] BUG: unable to handle kernel paging request at 0002ffa8
> [   30.017208] IP: __radix_tree_lookup+0x12/0xb0
> [   30.017235] *pdpt = 000000001eca5027 *pde = 0000000000000000 
> [   30.017271] Oops: 0000 [#1] SMP
> [   30.017293] Modules linked in: ext4 mbcache jbd2
> [   30.017352] CPU: 2 PID: 1204 Comm: systemd Not tainted 4.14.67+ #1
> [   30.017383] task: df601f80 task.stack: dafd8000
> [   30.017411] EIP: __radix_tree_lookup+0x12/0xb0
> [   30.017445] EFLAGS: 00010282 CPU: 2
> [   30.017468] EAX: 0002ffa4 EBX: b7ed2000 ECX: 00000000 EDX: 01ffffff
> [   30.017503] ESI: 00000000 EDI: 00000000 EBP: dafd9de4 ESP: dafd9dd0
> [   30.017534]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0069
> [   30.017571] CR0: 80050033 CR2: 0002ffa8 CR3: 1eca4000 CR4: 00042660
> [   30.017620] Call Trace:
> [   30.017642]  radix_tree_lookup_slot+0x11/0x30
> [   30.017673]  ? xen_set_pud+0xa0/0xa0
> [   30.017699]  find_get_entry+0x1d/0x110
> [   30.017723]  pagecache_get_page+0x1f/0x230
> [   30.017752]  lookup_swap_cache+0x35/0x110
> [   30.017778]  swap_readahead_detect+0x84/0x2f0
> [   30.017809]  do_swap_page+0x25b/0x8e0
> [   30.017837]  ? wp_page_copy+0x399/0x6b0
> [   30.017866]  ? kmap_atomic_prot+0x2b/0x180
> [   30.017892]  ? __raw_callee_save_xen_pte_val+0xc/0xc
> [   30.017925]  handle_mm_fault+0x468/0x9e0
> [   30.017951]  __do_page_fault+0x1ba/0x4e0
> [   30.017976]  ? __do_page_fault+0x4e0/0x4e0
> [   30.018008]  do_page_fault+0x37/0x100
> [   30.018032]  ? __do_page_fault+0x4e0/0x4e0
> [   30.018060]  common_exception+0x77/0x7e
> [   30.018084] EIP: 0xb7f0d39f
> [   30.018101] EFLAGS: 00010246 CPU: 2
> [   30.018124] EAX: b7ed2030 EBX: b7f20000 ECX: b7bf91b8 EDX: 00000002
> [   30.018158] ESI: b7f2055c EDI: b7f10e90 EBP: b7bf9260 ESP: b7bf9208
> [   30.018190]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b
> [   30.018220]  ? __do_page_fault+0x4e0/0x4e0
> [   30.018242] Code: 00 8b 03 c1 e8 1a 85 c0 74 be 0f 0b 8d b6 00 00 00 00 8d 
> bc 27 00 00 00 00 55 89 e5 57 56 53 83 ec 08 89 45 f0 89 4d ec 8b 45 f0 <8b> 
> 40 04 89 c1 83 e1 03 83 f9 01 75 71 89 c1 bf 40 00 00 00 83
> [   30.018415] EIP: __radix_tree_lookup+0x12/0xb0 SS:ESP: 0069:dafd9dd0
> [   30.018445] CR2: 000000000002ffa8
> [   30.018472] ---[ end trace c8ba97a241bb2040 ]---
> 
> isn't a (presumably indirect) result of
> 
> Sep  1 03:06:32.180094 (XEN) d28 L1TF-vulnerable L1e 8000000400000000 - 
> Shadowing
> 
> Jürgen's change to avoid split PTE writes would then only be
> papering over an active issue.

No, it isn't papering over the issue, but repairing it. See

https://bugzilla.kernel.org/show_bug.cgi?id=198497

which clearly states that this issue has been seen on bare metal, too.
On Xen its just much more frequent as the timing is different.


Juergen

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