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From: Andy Lutomirski <luto@kernel.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	richard.fellner@student.tugraz.at, moritz.lipp@iaik.tugraz.at,
	Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
	michael.schwarz@iaik.tugraz.at,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>,
	X86 ML <x86@kernel.org>
Subject: Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch)
Date: Sun, 26 Nov 2017 08:29:12 -0800	[thread overview]
Message-ID: <CALCETrUp=Cq0A8reEhXqmjeb_=C8yHS3-RTAH9TERGTxUG9AiQ@mail.gmail.com> (raw)
In-Reply-To: <2e4773b2-2cb3-284e-f0a7-3eaebc2676e5@linux.intel.com>

On Sun, Nov 26, 2017 at 8:24 AM, Dave Hansen
<dave.hansen@linux.intel.com> wrote:
> On 11/26/2017 08:10 AM, Andy Lutomirski wrote:
>>> As a side benefit, this shouldn't have magical interactions with the
>>> vsyscall page any more.
>>>
>>> Are there cases that this would get wrong?
>>>
>> Quick ping: did this get lost?
>
> It does drop a warning that the other version of the code has, but
> that's pretty minor.
>
> Basically, we need two checks:
>
>         pgd_userspace_access() (aka _PAGE_USER) and
>         pgdp_maps_userspace()
>
> The original code does pgd_userspace_access() in a top-level if and then
> the pgdp_maps_userspace() checks at the second level.  I think you are
> basically suggesting that we flip that.
>
> Logically, I'm sure we can make it work.  It's just a matter of needing
> to look at other things first.
>
> BTW, this comment is, I think incorrect:
>
>>   if (pgdp_maps_userspace(pgdp)) {
> ...
>>   } else {
>>     /*
>>      * We can get here due to vmalloc, a vmalloc fault, memory
>> hot-add, or initial setup
>>      * of kernelmode page tables.  Regardless of which particular code
>> path we're in,
>>      * these mappings should not be automatically propagated to the
>> usermode tables.
>>      */
>
> Since we pre-populated the entire kernel area's PGDs, I don't think
> we'll ever have a valid reason to be doing a set_pgd() again on the
> kernel area.

Right, forgot about that.  So it's just initial setup, then.

  reply	other threads:[~2017-11-26 16:29 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 [this message]
2018-01-05  4:16   ` Yisheng Xie
2018-01-05  5:18     ` Dave Hansen
2018-01-05  6:16       ` Yisheng Xie
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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