From: Dave Hansen <dave.hansen@intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Alison Schofield <alison.schofield@intel.com>,
Matthew Wilcox <willy@infradead.org>,
Dan Williams <dan.j.williams@intel.com>,
David Howells <dhowells@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
James Morris <jmorris@namei.org>, Ingo Molnar <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
kai.huang@intel.com, Jun Nakajima <jun.nakajima@intel.com>,
"Sakkinen, Jarkko" <jarkko.sakkinen@intel.com>,
keyrings@vger.kernel.org,
LSM List <linux-security-module@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, X86 ML <x86@kernel.org>
Subject: Re: [RFC v2 00/13] Multi-Key Total Memory Encryption API (MKTME)
Date: Thu, 6 Dec 2018 11:31:37 -0800 [thread overview]
Message-ID: <7116c946-4e4b-c7cf-e28a-1a2b932f61f2@intel.com> (raw)
In-Reply-To: <CALCETrVPhay-ziRVjL9dDCwJQHhr4HfG5aGJzYh06k6HEMZTiQ@mail.gmail.com>
On 12/6/18 11:10 AM, Andy Lutomirski wrote:
>> On Dec 6, 2018, at 7:39 AM, Dave Hansen <dave.hansen@intel.com> wrote:
>>The coherency is "fine" unless you have writeback of an older
>> cacheline that blows away newer data. CPUs that support MKTME are
>> guaranteed to never do writeback of the lines that could be established
>> speculatively or from prefetching.
>
> How is that sufficient? Suppose I have some physical page mapped with
> keys 1 and 2. #1 is logically live and I write to it. Then I prefetch
> or otherwise populate mapping 2 into the cache (in the S state,
> presumably). Now I clflush mapping 1 and read 2. It contains garbage
> in the cache, but the garbage in the cache is inconsistent with the
> garbage in memory. This can’t be a good thing, even if no writeback
> occurs.
>
> I suppose the right fix is to clflush the old mapping and then to zero
> the new mapping.
Yep. Practically, you need to write to the new mapping to give it any
meaning. Those writes effectively blow away any previously cached,
garbage contents.
I think you're right, though, that the cached data might not be
_consistent_ with what is in memory. It feels really dirty, but I can't
think of any problems that it actually causes.
next prev parent reply other threads:[~2018-12-06 19:31 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 7:39 [RFC v2 00/13] Multi-Key Total Memory Encryption API (MKTME) Alison Schofield
2018-12-04 7:39 ` [RFC v2 01/13] x86/mktme: Document the MKTME APIs Alison Schofield
2018-12-05 18:11 ` Andy Lutomirski
2018-12-05 19:22 ` Alison Schofield
2018-12-05 23:35 ` Andy Lutomirski
2018-12-06 8:04 ` Sakkinen, Jarkko
2018-12-04 7:39 ` [RFC v2 02/13] mm: Generalize the mprotect implementation to support extensions Alison Schofield
2018-12-06 8:08 ` Sakkinen, Jarkko
2018-12-04 7:39 ` [RFC v2 03/13] syscall/x86: Wire up a new system call for memory encryption keys Alison Schofield
2018-12-04 7:39 ` [RFC v2 04/13] x86/mm: Add helper functions for MKTME " Alison Schofield
2018-12-04 9:14 ` Peter Zijlstra
2018-12-05 5:49 ` Alison Schofield
2018-12-04 15:35 ` Andy Lutomirski
2018-12-05 5:52 ` Alison Schofield
2018-12-06 8:31 ` Sakkinen, Jarkko
2018-12-04 7:39 ` [RFC v2 05/13] x86/mm: Set KeyIDs in encrypted VMAs Alison Schofield
2018-12-06 8:37 ` Sakkinen, Jarkko
2018-12-04 7:39 ` [RFC v2 06/13] mm: Add the encrypt_mprotect() system call Alison Schofield
2018-12-06 8:38 ` Sakkinen, Jarkko
2018-12-04 7:39 ` [RFC v2 07/13] x86/mm: Add helpers for reference counting encrypted VMAs Alison Schofield
2018-12-04 8:58 ` Peter Zijlstra
2018-12-05 5:28 ` Alison Schofield
2018-12-04 7:39 ` [RFC v2 08/13] mm: Use reference counting for " Alison Schofield
2018-12-04 7:39 ` [RFC v2 09/13] mm: Restrict memory encryption to anonymous VMA's Alison Schofield
2018-12-04 9:10 ` Peter Zijlstra
2018-12-05 5:30 ` Alison Schofield
2018-12-05 9:07 ` Peter Zijlstra
2018-12-04 7:39 ` [RFC v2 10/13] keys/mktme: Add the MKTME Key Service type for memory encryption Alison Schofield
2018-12-06 8:51 ` Sakkinen, Jarkko
2018-12-06 8:54 ` Sakkinen, Jarkko
2018-12-06 15:11 ` Dave Hansen
2018-12-06 22:56 ` Sakkinen, Jarkko
2018-12-04 7:39 ` [RFC v2 11/13] keys/mktme: Program memory encryption keys on a system wide basis Alison Schofield
2018-12-04 9:21 ` Peter Zijlstra
2018-12-04 9:50 ` Kirill A. Shutemov
2018-12-05 5:44 ` Alison Schofield
2018-12-05 5:43 ` Alison Schofield
2018-12-05 9:10 ` Peter Zijlstra
2018-12-05 17:26 ` Alison Schofield
2018-12-04 7:39 ` [RFC v2 12/13] keys/mktme: Save MKTME data if kernel cmdline parameter allows Alison Schofield
2018-12-04 9:22 ` Peter Zijlstra
2018-12-07 2:14 ` Huang, Kai
2018-12-07 3:42 ` Alison Schofield
2018-12-07 6:39 ` Jarkko Sakkinen
2018-12-07 6:45 ` Jarkko Sakkinen
2018-12-07 11:47 ` Kirill A. Shutemov
2018-12-04 7:40 ` [RFC v2 13/13] keys/mktme: Support CPU Hotplug for MKTME keys Alison Schofield
2018-12-04 9:28 ` Peter Zijlstra
2018-12-05 5:32 ` Alison Schofield
2018-12-04 9:31 ` Peter Zijlstra
2018-12-05 5:36 ` Alison Schofield
2018-12-04 9:25 ` [RFC v2 00/13] Multi-Key Total Memory Encryption API (MKTME) Peter Zijlstra
2018-12-04 9:46 ` Kirill A. Shutemov
2018-12-05 20:32 ` Sakkinen, Jarkko
2018-12-06 11:22 ` Kirill A. Shutemov
2018-12-06 14:59 ` Dave Hansen
2018-12-07 10:12 ` Huang, Kai
2018-12-06 21:23 ` Sakkinen, Jarkko
2018-12-07 11:54 ` Kirill A. Shutemov
2018-12-04 19:19 ` Andy Lutomirski
2018-12-04 20:00 ` Andy Lutomirski
2018-12-04 20:32 ` Dave Hansen
2018-12-05 22:19 ` Sakkinen, Jarkko
2018-12-07 2:05 ` Huang, Kai
2018-12-07 6:48 ` Jarkko Sakkinen
2018-12-07 11:57 ` Kirill A. Shutemov
2018-12-07 21:59 ` Sakkinen, Jarkko
2018-12-07 23:45 ` Sakkinen, Jarkko
2018-12-07 23:48 ` Andy Lutomirski
2018-12-08 1:33 ` Huang, Kai
2018-12-08 3:53 ` Sakkinen, Jarkko
2018-12-12 15:31 ` Sakkinen, Jarkko
2018-12-12 16:29 ` Andy Lutomirski
2018-12-12 16:43 ` Sakkinen, Jarkko
2018-12-12 23:27 ` Huang, Kai
2018-12-13 5:49 ` Sakkinen, Jarkko
2018-12-13 5:52 ` Sakkinen, Jarkko
2018-12-12 23:24 ` Huang, Kai
2018-12-07 23:35 ` Eric Rannaud
2018-12-05 23:49 ` Dave Hansen
2018-12-06 1:09 ` Andy Lutomirski
2018-12-06 1:25 ` Dan Williams
2018-12-06 15:39 ` Dave Hansen
2018-12-06 19:10 ` Andy Lutomirski
2018-12-06 19:31 ` Dave Hansen [this message]
2018-12-07 1:55 ` Huang, Kai
2018-12-07 4:23 ` Dave Hansen
2018-12-07 23:53 ` Andy Lutomirski
2018-12-08 1:11 ` Dave Hansen
2018-12-08 2:07 ` Huang, Kai
2018-12-05 20:30 ` Sakkinen, Jarkko
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