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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CA+55aFw0OF0JSio47KVPrAz6CaJuX8kEvMk0DWVG2HZzRFr_+Q@mail.gmail.com \
--to=torvalds@linux-foundation.org \
--cc=a.p.zijlstra@chello.nl \
--cc=brgerst@gmail.com \
--cc=dave.hansen@linux.intel.com \
--cc=dvlasenk@redhat.com \
--cc=hpa@zytor.com \
--cc=jpoimboe@redhat.com \
--cc=keescook@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mingo@kernel.org \
--cc=tglx@linutronix.de \
--cc=thgarnie@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).