From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"H. Peter Anvin" <hpa@zytor.com>,
borisBrian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Thomas Garnier <thgarnie@google.com>,
Kees Cook <keescook@google.com>
Subject: Re: [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables
Date: Wed, 1 Nov 2017 15:28:48 -0700 [thread overview]
Message-ID: <CA+55aFw0OF0JSio47KVPrAz6CaJuX8kEvMk0DWVG2HZzRFr_+Q@mail.gmail.com> (raw)
In-Reply-To: <d7cb1705-5ef0-5f6e-b1cf-e3f28e998477@linux.intel.com>
On Wed, Nov 1, 2017 at 3:14 PM, Dave Hansen <dave.hansen@linux.intel.com> wrote:
>
> I ran some quick tests. When CONFIG_KAISER=y, but "echo 0 >
> kaiser-enabled", the tests that I ran were within the noise vs. a
> vanilla kernel, and that's with *zero* optimization.
I guess the optimal version just ends up switching between two
different entrypoints for the on/off case.
And the not-quite-as-aggressive, but almost-optimal version would just
be a two-byte asm alternative with an unconditional branch to the
movcr3 code and back, and is turned into a noop when it's off.
But since 99%+ of the cost is going to be that cr3 write, even the
stupid "just load value and branch over the cr3 conditionally" is
going to make things hard to measure.
Linus
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next prev parent reply other threads:[~2017-11-01 22:28 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 22:31 [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables Dave Hansen
2017-10-31 22:31 ` [PATCH 01/23] x86, kaiser: prepare assembly for entry/exit CR3 switching Dave Hansen
2017-11-01 0:43 ` Brian Gerst
2017-11-01 1:08 ` Dave Hansen
2017-11-01 18:18 ` Borislav Petkov
2017-11-01 18:27 ` Dave Hansen
2017-11-01 20:42 ` Borislav Petkov
2017-11-01 21:01 ` Thomas Gleixner
2017-11-01 22:58 ` Dave Hansen
2017-10-31 22:31 ` [PATCH 02/23] x86, kaiser: do not set _PAGE_USER for init_mm page tables Dave Hansen
2017-11-01 21:11 ` Thomas Gleixner
2017-11-01 21:24 ` Andy Lutomirski
2017-11-01 21:28 ` Thomas Gleixner
2017-11-01 21:52 ` Dave Hansen
2017-11-01 22:11 ` Thomas Gleixner
2017-11-01 22:12 ` Linus Torvalds
2017-11-01 22:20 ` Thomas Gleixner
2017-11-01 22:45 ` Kees Cook
2017-11-02 7:10 ` Andy Lutomirski
2017-11-02 11:33 ` Thomas Gleixner
2017-11-02 11:59 ` Andy Lutomirski
2017-11-02 12:56 ` Thomas Gleixner
2017-11-02 16:38 ` Dave Hansen
2017-11-02 18:19 ` Andy Lutomirski
2017-11-02 18:24 ` Thomas Gleixner
2017-11-02 18:24 ` Linus Torvalds
2017-11-02 18:40 ` Thomas Gleixner
2017-11-02 18:57 ` Linus Torvalds
2017-11-02 21:41 ` Thomas Gleixner
2017-11-02 7:07 ` Andy Lutomirski
2017-11-02 11:21 ` Thomas Gleixner
2017-10-31 22:31 ` [PATCH 03/23] x86, kaiser: disable global pages Dave Hansen
2017-11-01 21:18 ` Thomas Gleixner
2017-11-01 22:12 ` Dave Hansen
2017-11-01 22:28 ` Thomas Gleixner
2017-10-31 22:31 ` [PATCH 04/23] x86, tlb: make CR4-based TLB flushes more robust Dave Hansen
2017-11-01 8:01 ` Andy Lutomirski
2017-11-01 10:11 ` Kirill A. Shutemov
2017-11-01 10:38 ` Andy Lutomirski
2017-11-01 10:56 ` Kirill A. Shutemov
2017-11-01 11:18 ` Andy Lutomirski
2017-11-01 22:21 ` Dave Hansen
2017-11-01 21:25 ` Thomas Gleixner
2017-11-01 22:24 ` Dave Hansen
2017-11-01 22:30 ` Thomas Gleixner
2017-10-31 22:31 ` [PATCH 05/23] x86, mm: document X86_CR4_PGE toggling behavior Dave Hansen
2017-10-31 23:31 ` Kees Cook
2017-10-31 22:31 ` [PATCH 06/23] x86, kaiser: introduce user-mapped percpu areas Dave Hansen
2017-11-01 21:47 ` Thomas Gleixner
2017-10-31 22:31 ` [PATCH 07/23] x86, kaiser: unmap kernel from userspace page tables (core patch) Dave Hansen
2017-10-31 22:32 ` [PATCH 08/23] x86, kaiser: only populate shadow page tables for userspace Dave Hansen
2017-10-31 23:35 ` Kees Cook
2017-10-31 22:32 ` [PATCH 09/23] x86, kaiser: allow NX to be set in p4d/pgd Dave Hansen
2017-10-31 22:32 ` [PATCH 10/23] x86, kaiser: make sure static PGDs are 8k in size Dave Hansen
2017-10-31 22:32 ` [PATCH 11/23] x86, kaiser: map GDT into user page tables Dave Hansen
2017-10-31 22:32 ` [PATCH 12/23] x86, kaiser: map dynamically-allocated LDTs Dave Hansen
2017-11-01 8:00 ` Andy Lutomirski
2017-11-01 8:06 ` Ingo Molnar
2017-10-31 22:32 ` [PATCH 13/23] x86, kaiser: map espfix structures Dave Hansen
2017-10-31 22:32 ` [PATCH 14/23] x86, kaiser: map entry stack variables Dave Hansen
2017-10-31 22:32 ` [PATCH 15/23] x86, kaiser: map trace interrupt entry Dave Hansen
2017-10-31 22:32 ` [PATCH 16/23] x86, kaiser: map debug IDT tables Dave Hansen
2017-10-31 22:32 ` [PATCH 17/23] x86, kaiser: map virtually-addressed performance monitoring buffers Dave Hansen
2017-10-31 22:32 ` [PATCH 18/23] x86, mm: Move CR3 construction functions Dave Hansen
2017-10-31 22:32 ` [PATCH 19/23] x86, mm: remove hard-coded ASID limit checks Dave Hansen
2017-10-31 22:32 ` [PATCH 20/23] x86, mm: put mmu-to-h/w ASID translation in one place Dave Hansen
2017-10-31 22:32 ` [PATCH 21/23] x86, pcid, kaiser: allow flushing for future ASID switches Dave Hansen
2017-11-01 8:03 ` Andy Lutomirski
2017-11-01 14:17 ` Dave Hansen
2017-11-01 20:31 ` Andy Lutomirski
2017-11-01 20:59 ` Dave Hansen
2017-11-01 21:04 ` Andy Lutomirski
2017-11-01 21:06 ` Dave Hansen
2017-10-31 22:32 ` [PATCH 22/23] x86, kaiser: use PCID feature to make user and kernel switches faster Dave Hansen
2017-10-31 22:32 ` [PATCH 23/23] x86, kaiser: add Kconfig Dave Hansen
2017-10-31 23:59 ` Kees Cook
2017-11-01 9:07 ` Borislav Petkov
2017-10-31 23:27 ` [PATCH 00/23] KAISER: unmap most of the kernel from userspace page tables Linus Torvalds
2017-10-31 23:44 ` Dave Hansen
2017-11-01 0:21 ` Dave Hansen
2017-11-01 7:59 ` Andy Lutomirski
2017-11-01 16:08 ` Linus Torvalds
2017-11-01 17:31 ` Dave Hansen
2017-11-01 17:58 ` Randy Dunlap
2017-11-01 18:27 ` Linus Torvalds
2017-11-01 18:46 ` Dave Hansen
2017-11-01 19:05 ` Linus Torvalds
2017-11-01 20:33 ` Andy Lutomirski
2017-11-02 7:32 ` Andy Lutomirski
2017-11-02 7:54 ` Andy Lutomirski
2017-11-01 15:53 ` Dave Hansen
2017-11-01 8:54 ` Ingo Molnar
2017-11-01 14:09 ` Thomas Gleixner
2017-11-01 22:14 ` Dave Hansen
2017-11-01 22:28 ` Linus Torvalds [this message]
2017-11-02 8:03 ` Peter Zijlstra
2017-11-03 11:07 ` Kirill A. Shutemov
2017-11-02 19:01 ` Will Deacon
2017-11-02 19:38 ` Dave Hansen
2017-11-03 13:41 ` Will Deacon
2017-11-22 16:19 ` Pavel Machek
2017-11-23 10:47 ` Pavel Machek
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