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From: Yisheng Xie <xieyisheng1@huawei.com>
To: Dave Hansen <dave.hansen@linux.intel.com>,
	<linux-kernel@vger.kernel.org>
Cc: <linux-mm@kvack.org>, <richard.fellner@student.tugraz.at>,
	<moritz.lipp@iaik.tugraz.at>, <daniel.gruss@iaik.tugraz.at>,
	<michael.schwarz@iaik.tugraz.at>, <luto@kernel.org>,
	<torvalds@linux-foundation.org>, <keescook@google.com>,
	<hughd@google.com>, <x86@kernel.org>
Subject: Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch)
Date: Fri, 5 Jan 2018 14:16:38 +0800	[thread overview]
Message-ID: <bda85c5e-d2be-f4ac-e2b4-4ef01d5a01a5@huawei.com> (raw)
In-Reply-To: <93776eb2-b6d4-679a-280c-8ba558a69c34@linux.intel.com>

Hi Dave,

On 2018/1/5 13:18, Dave Hansen wrote:
> On 01/04/2018 08:16 PM, Yisheng Xie wrote:
>>> === Page Table Poisoning ===
>>>
>>> KAISER has two copies of the page tables: one for the kernel and
>>> one for when running in userspace.  
>>
>> So, we have 2 page table, thinking about this case:
>> If _ONE_ process includes _TWO_ threads, one run in user space, the other
>> run in kernel, they can run in one core with Hyper-Threading, right?
> 
> Yes.
> 
>> So both userspace and kernel space is valid, right? And for one core
>> with Hyper-Threading, they may share TLB, so the timing problem
>> described in the paper may still exist?
> 
> No.  The TLB is managed per logical CPU (hyperthread), as is the CR3
> register that points to the page tables.  Two threads running the same
> process might use the same CR3 _value_, but that does not mean they
> share TLB entries.

Get it, and thanks for your explain.

BTW, we have just reported a bug caused by kaiser[1], which looks like
caused by SMEP. Could you please help to have a look?

[1] https://lkml.org/lkml/2018/1/5/3

Thanks
Yisheng

> 
> One thread *can* be in the kernel with the kernel page tables while the
> other is in userspace with the user page tables active.  They will even
> use a different PCID/ASID for the same page tables normally.
> 
>> Can this case still be protected by KAISER?
> 
> Yes.
> 
> .
> 

  reply	other threads:[~2018-01-05  6:17 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-23  0:34 [PATCH 00/23] [v4] KAISER: unmap most of the kernel from userspace page tables Dave Hansen
2017-11-23  0:34 ` [PATCH 01/23] x86, kaiser: disable global pages by default with KAISER Dave Hansen
2017-11-23  0:34 ` [PATCH 02/23] x86, kaiser: prepare assembly for entry/exit CR3 switching Dave Hansen
2017-11-23  0:34 ` [PATCH 03/23] x86, kaiser: introduce user-mapped per-cpu areas Dave Hansen
2017-11-23  0:34 ` [PATCH 04/23] x86, kaiser: mark per-cpu data structures required for entry/exit Dave Hansen
2017-11-23  0:34 ` [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch) Dave Hansen
2017-11-23  4:07   ` Andy Lutomirski
2017-11-26 16:10     ` Andy Lutomirski
2017-11-26 16:24       ` Dave Hansen
2017-11-26 16:29         ` Andy Lutomirski
2018-01-05  4:16   ` Yisheng Xie
2018-01-05  5:18     ` Dave Hansen
2018-01-05  6:16       ` Yisheng Xie [this message]
2018-01-05  6:29         ` Dave Hansen
2018-01-05 11:49           ` Andrea Arcangeli
2018-01-05 18:19           ` Jiri Kosina
2018-01-05 19:00             ` Jiri Kosina
2018-01-05 19:03             ` Dave Hansen
2018-01-05 19:17               ` Jiri Kosina
2018-01-05 19:18                 ` Jiri Kosina
2018-01-05 19:55                 ` Andrea Arcangeli
2018-01-05 21:07                 ` Dave Hansen
2018-01-05 21:14                   ` Jiri Kosina
2018-01-05 21:29                     ` Andy Lutomirski
2018-01-05 22:48                     ` Hugh Dickins
2018-01-06  4:54             ` Hanjun Guo
2018-01-06  6:06               ` Dave Hansen
2018-01-06  6:28                 ` Hanjun Guo
2018-01-06  6:53                   ` Hanjun Guo
2018-01-06  7:55                     ` Dave Hansen
2018-01-06  8:42                       ` Hanjun Guo
2018-01-06  7:51                   ` Dave Hansen
2018-01-06 17:22                     ` Andrea Arcangeli
2017-11-23  0:34 ` [PATCH 06/23] x86, kaiser: allow NX poison to be set in p4d/pgd Dave Hansen
2017-11-23  0:34 ` [PATCH 07/23] x86, kaiser: make sure static PGDs are 8k in size Dave Hansen
2017-11-23  0:34 ` [PATCH 08/23] x86, kaiser: map cpu entry area Dave Hansen
2017-11-23  0:34 ` [PATCH 09/23] x86, kaiser: map dynamically-allocated LDTs Dave Hansen
2017-11-23 19:42   ` Eric Biggers
2017-11-23 20:12     ` Andy Lutomirski
2017-11-23  0:34 ` [PATCH 10/23] x86, kaiser: map espfix structures Dave Hansen
2017-11-23  0:34 ` [PATCH 11/23] x86, kaiser: map entry stack variables Dave Hansen
2017-11-23  3:31   ` Andy Lutomirski
2017-11-23 15:37     ` Dave Hansen
2017-11-23 15:55       ` Andy Lutomirski
2017-11-23  0:35 ` [PATCH 12/23] x86, kaiser: map virtually-addressed performance monitoring buffers Dave Hansen
2017-11-23  0:35 ` [PATCH 13/23] x86, mm: Move CR3 construction functions Dave Hansen
2017-11-23  0:35 ` [PATCH 14/23] x86, mm: remove hard-coded ASID limit checks Dave Hansen
2017-11-23  0:35 ` [PATCH 15/23] x86, mm: put mmu-to-h/w ASID translation in one place Dave Hansen
2017-11-23  0:35 ` [PATCH 16/23] x86, pcid, kaiser: allow flushing for future ASID switches Dave Hansen
2017-11-23  0:35 ` [PATCH 17/23] x86, kaiser: use PCID feature to make user and kernel switches faster Dave Hansen
2017-11-23  0:35 ` [PATCH 18/23] x86, kaiser: disable native VSYSCALL Dave Hansen
2017-11-23  0:35 ` [PATCH 19/23] x86, kaiser: add debugfs file to turn KAISER on/off at runtime Dave Hansen
2017-11-23  0:35 ` [PATCH 20/23] x86, kaiser: add a function to check for KAISER being enabled Dave Hansen
2017-11-25  1:23   ` Eduardo Valentin
2017-11-23  0:35 ` [PATCH 21/23] x86, kaiser: un-poison PGDs at runtime Dave Hansen
2017-11-25  1:17   ` Eduardo Valentin
2017-11-23  0:35 ` [PATCH 22/23] x86, kaiser: allow KAISER to be enabled/disabled " Dave Hansen
2017-11-23  0:35 ` [PATCH 23/23] x86, kaiser: add Kconfig Dave Hansen
2017-11-23  7:23 ` [PATCH 00/23] [v4] KAISER: unmap most of the kernel from userspace page tables Ingo Molnar
2017-11-23  7:27 ` Ingo Molnar
2017-11-23  7:32   ` Ingo Molnar
2017-11-23 15:02     ` Dave Hansen
2017-11-23 16:20 ` Dave Hansen
2017-11-24  6:35   ` Ingo Molnar
2017-11-24  6:41     ` Dave Hansen
2017-11-24  7:33       ` Ingo Molnar

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