From: Andy Lutomirski <luto@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Hansen <dave.hansen@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Andy Lutomirsky <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bpetkov@suse.de>,
Greg KH <gregkh@linuxfoundation.org>,
Kees Cook <keescook@google.com>, Hugh Dickins <hughd@google.com>,
Brian Gerst <brgerst@gmail.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
David Laight <David.Laight@aculab.com>,
Eduardo Valentin <eduval@amazon.com>,
"Liguori, Anthony" <aliguori@amazon.com>,
Will Deacon <will.deacon@arm.com>, linux-mm <linux-mm@kvack.org>
Subject: Re: [patch 13/16] x86/ldt: Introduce LDT write fault handler
Date: Tue, 12 Dec 2017 13:35:28 -0800 [thread overview]
Message-ID: <CALCETrVt8zzfoszh83N0dT9TEax3pr+HLauprKWD2FssvFYXYA@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1712122124320.2289@nanos>
On Tue, Dec 12, 2017 at 12:37 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Tue, 12 Dec 2017, Dave Hansen wrote:
>
>> On 12/12/2017 11:21 AM, Thomas Gleixner wrote:
>> > The only critical interaction is the return to user path (user CS/SS) and
>> > we made sure with the LAR touching that these are precached in the CPU
>> > before we go into fragile exit code.
>>
>> How do we make sure that it _stays_ cached?
>>
>> Surely there is weird stuff like WBINVD or SMI's that can come at very
>> inconvenient times and wipe it out of the cache.
>
> This does not look like cache in the sense of memory cache. It seems to be
> CPU internal state and I just stuffed WBINVD and alternatively CLFLUSH'ed
> the entries after the 'touch' via LAR. Still works.
>
There *must* be some weird bug in this series. I find it very hard to
believe that x86 CPUs have a magic cache that caches any part of a
not-actually-in-a-segment-register descriptor entry.
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next prev parent reply other threads:[~2017-12-12 21:35 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-12 17:32 [patch 00/16] x86/ldt: Use a VMA based read only mapping Thomas Gleixner
2017-12-12 17:32 ` [patch 01/16] arch: Allow arch_dup_mmap() to fail Thomas Gleixner
2017-12-12 17:32 ` [patch 02/16] x86/ldt: Rework locking Thomas Gleixner
2017-12-12 17:32 ` [patch 03/16] x86/ldt: Prevent ldt inheritance on exec Thomas Gleixner
2017-12-12 17:32 ` [patch 04/16] mm/softdirty: Move VM_SOFTDIRTY into high bits Thomas Gleixner
2017-12-12 17:32 ` [patch 05/16] mm: Allow special mappings with user access cleared Thomas Gleixner
2017-12-12 18:00 ` Andy Lutomirski
2017-12-12 18:05 ` Peter Zijlstra
2017-12-12 18:06 ` Andy Lutomirski
2017-12-12 18:25 ` Peter Zijlstra
2017-12-13 12:22 ` Peter Zijlstra
2017-12-13 12:57 ` Kirill A. Shutemov
2017-12-13 14:34 ` Peter Zijlstra
2017-12-13 14:43 ` Kirill A. Shutemov
2017-12-13 15:00 ` Peter Zijlstra
2017-12-13 15:04 ` Peter Zijlstra
2017-12-13 15:14 ` Dave Hansen
2017-12-13 15:32 ` Peter Zijlstra
2017-12-13 15:47 ` Dave Hansen
2017-12-13 15:54 ` Peter Zijlstra
2017-12-13 18:08 ` Linus Torvalds
2017-12-13 18:21 ` Dave Hansen
2017-12-13 18:23 ` Linus Torvalds
2017-12-13 18:31 ` Andy Lutomirski
2017-12-13 18:32 ` Peter Zijlstra
2017-12-13 18:35 ` Linus Torvalds
2017-12-14 4:53 ` Aneesh Kumar K.V
2017-12-13 21:50 ` Matthew Wilcox
2017-12-13 22:12 ` Peter Zijlstra
2017-12-14 0:10 ` Matthew Wilcox
2017-12-14 0:16 ` Andy Lutomirski
2017-12-12 17:32 ` [patch 06/16] mm: Provide vm_special_mapping::close Thomas Gleixner
2017-12-12 17:32 ` [patch 07/16] selftest/x86: Implement additional LDT selftests Thomas Gleixner
2017-12-12 17:32 ` [patch 08/16] selftests/x86/ldt_gdt: Prepare for access bit forced Thomas Gleixner
2017-12-12 17:32 ` [patch 09/16] mm: Make populate_vma_page_range() available Thomas Gleixner
2017-12-12 17:32 ` [patch 10/16] x86/ldt: Do not install LDT for kernel threads Thomas Gleixner
2017-12-12 17:57 ` Andy Lutomirski
2017-12-12 17:32 ` [patch 11/16] x86/ldt: Force access bit for CS/SS Thomas Gleixner
2017-12-12 18:03 ` Andy Lutomirski
2017-12-12 18:09 ` Peter Zijlstra
2017-12-12 18:10 ` Andy Lutomirski
2017-12-12 18:22 ` Andy Lutomirski
2017-12-12 18:29 ` Peter Zijlstra
2017-12-12 18:41 ` Thomas Gleixner
2017-12-12 19:04 ` Peter Zijlstra
2017-12-12 19:05 ` Linus Torvalds
2017-12-12 19:26 ` Andy Lutomirski
2017-12-19 12:10 ` David Laight
2017-12-12 17:32 ` [patch 12/16] x86/ldt: Reshuffle code Thomas Gleixner
2017-12-12 17:32 ` [patch 13/16] x86/ldt: Introduce LDT write fault handler Thomas Gleixner
2017-12-12 17:58 ` Andy Lutomirski
2017-12-12 18:19 ` Peter Zijlstra
2017-12-12 18:43 ` Thomas Gleixner
2017-12-12 19:01 ` Linus Torvalds
2017-12-12 19:21 ` Thomas Gleixner
2017-12-12 19:51 ` Linus Torvalds
2017-12-12 20:21 ` Dave Hansen
2017-12-12 20:37 ` Thomas Gleixner
2017-12-12 21:35 ` Andy Lutomirski [this message]
2017-12-12 21:42 ` Thomas Gleixner
2017-12-12 21:41 ` Thomas Gleixner
2017-12-12 21:46 ` Thomas Gleixner
2017-12-12 22:25 ` Peter Zijlstra
2017-12-12 17:32 ` [patch 14/16] x86/ldt: Prepare for VMA mapping Thomas Gleixner
2017-12-12 17:32 ` [patch 15/16] x86/ldt: Add VMA management code Thomas Gleixner
2017-12-12 17:32 ` [patch 16/16] x86/ldt: Make it read only VMA mapped Thomas Gleixner
2017-12-12 18:03 ` [patch 00/16] x86/ldt: Use a VMA based read only mapping Andy Lutomirski
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