LKML Archive on lore.kernel.org
 help / color / Atom feed
From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>,
	"H . Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Markus T Metzger <markus.t.metzger@intel.com>,
	Ravi Shankar <ravi.v.shankar@intel.com>,
	"Chang S . Bae" <chang.seok.bae@intel.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: [v3 00/12] x86: Enable FSGSBASE instructions
Date: Tue, 23 Oct 2018 11:42:22 -0700
Message-ID: <20181023184234.14025-1-chang.seok.bae@intel.com> (raw)

FSGSBASE is a 64-bit instruction set to allow read/write FS/GSBASE from
any privileges. Since introduced in Ivybridge, enabling efforts has been
revolving in a quite long period of time, for various reasons [2,3,4].
After the extended discussions [1], the new ABIs are finally introduced to
customize FS/GSBASE separately from the selector.

Benefits:
Some performance benefit in context switch is expected by skipping MSR
write for GSBASE. User-level programs (such as JAVA-based) may benefit
from avoiding system calls to edit FS/GSBASE.

Major changes in the kernel:
* In a context switch, a thread's FS/GSBASE will be secured regardless of
its selector, base on the discussion [1].
* (Subsequently) ptracer should expect a divergence of FS/GS index and
base values. There was a controversial debate on the concerns for a
backward compatibility (mostly for GDB. [7,8]). We finally concluded it is
insignificant in real usages.
* On the paranoid_entry, GSBASE is updated to point the per_CPU base and
the original GSBASE is restored at the exit.

Virtualization:
A FSGSBASE-enabled VM can be located on a host either with HW
virtualization or with SW emulation. KVM advertises FSGSBASE when
physical CPU has. The emulation is supported in QEMU/TCG [5]. In a pool of
the mixed systems, VMM may disable FSGSBASE for seamless VM migrations [6].

Update from v2 [10]:
* Separate out the preparatory patches [11] (now merged to the tip)
* Bisect the paranoid_entry update patch
* Edit minor nits

Updates from v1 [9]:
* Update the GSBASE update mechanism on the paranoid entry/exit.
* Exclude ptracer backward compatibility patches.
* Include FSGSBASE documentation and enumerating capability
for user space
* Add the TAINT_INSECURE flag.

[1] Recent discussion on LKML:
https://marc.info/?t=150147053700001&r=1&w=2
[2] Andy Lutomirski’s patchwork work :
https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/log/?h=x86/fsgsbase
[3] Patchset shown in 2016:
https://lore.kernel.org/patchwork/patch/660520
[4] Patchset shown in 2014:
https://lore.kernel.org/patchwork/patch/460288
[5] QEMU with FSGSBASE emulation:
https://github.com/qemu/qemu/blob/026aaf47c02b79036feb830206cfebb2a726510d/target/i386/translate.c#L8186
[6] 5-level EPT:
http://lkml.kernel.org/r/9ddf602b-6c8b-8c1e-ab46-07ed12366593@redhat.com
[7] RR/FSGSBASE:
https://mail.mozilla.org/pipermail/rr-dev/2018-March/000616.html
[8] CRIU/FSGSBASE:
https://lists.openvz.org/pipermail/criu/2018-March/040654.html
[9] Version 1:
https://lore.kernel.org/patchwork/cover/934843
[10] Version 2:
https://lore.kernel.org/patchwork/cover/912063
[11] x86: infra to enable FSGSBASE
https://lore.kernel.org/patchwork/cover/988180

Andi Kleen (3):
  x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions
  x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2
  x86/fsgsbase/64: Add documentation for FSGSBASE

Andy Lutomirski (4):
  x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE
  x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is
    on
  selftests/x86/fsgsbase: Test WRGSBASE
  x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit

Chang S. Bae (5):
  taint: Introduce a new taint flag (insecure)
  x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions
  x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions
    if available
  x86/fsgsbase/64: Introduce the new FIND_PERCPU_BASE macro
  x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry

 .../admin-guide/kernel-parameters.txt         |   2 +
 Documentation/sysctl/kernel.txt               |   1 +
 Documentation/x86/fsgs.txt                    | 104 +++++++++++++
 arch/x86/entry/entry_64.S                     |  73 +++++++--
 arch/x86/include/asm/fsgsbase.h               | 140 +++++++++++++++++-
 arch/x86/include/asm/inst.h                   |  15 ++
 arch/x86/include/uapi/asm/hwcap2.h            |   3 +
 arch/x86/kernel/cpu/common.c                  |  22 +++
 arch/x86/kernel/process_64.c                  | 128 +++++++++++++---
 include/linux/kernel.h                        |   3 +-
 kernel/panic.c                                |   1 +
 tools/testing/selftests/x86/fsgsbase.c        | 110 +++++++++++++-
 12 files changed, 556 insertions(+), 46 deletions(-)
 create mode 100644 Documentation/x86/fsgs.txt

--
2.19.1


             reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-23 18:42 Chang S. Bae [this message]
2018-10-23 18:42 ` [v3 01/12] taint: Introduce a new taint flag (insecure) Chang S. Bae
2018-10-24 18:50   ` Andy Lutomirski
2018-10-23 18:42 ` [v3 02/12] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2018-10-24 18:51   ` Andy Lutomirski
2018-10-23 18:42 ` [v3 03/12] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2018-10-24 18:53   ` Andy Lutomirski
2018-10-24 19:21     ` Andi Kleen
2018-10-25 23:14       ` Andy Lutomirski
2018-10-25 23:31         ` Linus Torvalds
2018-10-26  0:09           ` Andy Lutomirski
2018-10-23 18:42 ` [v3 04/12] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions Chang S. Bae
2018-10-24 19:16   ` Andy Lutomirski
2018-10-24 19:41     ` [Xen-devel] " Andrew Cooper
2018-10-25  6:09       ` Juergen Gross
2018-10-25 23:08         ` Andrew Cooper
2018-10-25 23:11           ` Andy Lutomirski
2018-10-25 23:14             ` Andrew Cooper
2018-10-25  7:32     ` Bae, Chang Seok
2018-10-25 23:00       ` Andy Lutomirski
2018-10-25 23:03         ` Bae, Chang Seok
2018-10-25 23:16     ` Andy Lutomirski
2018-10-23 18:42 ` [v3 05/12] x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on Chang S. Bae
2018-10-24 19:21   ` Andy Lutomirski
2018-10-24 19:36     ` Bae, Chang Seok
2018-10-23 18:42 ` [v3 06/12] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available Chang S. Bae
2018-10-23 18:42 ` [v3 07/12] x86/fsgsbase/64: Introduce the new FIND_PERCPU_BASE macro Chang S. Bae
2018-10-26  0:25   ` Andy Lutomirski
2018-10-26  0:59     ` Nadav Amit
2018-10-23 18:42 ` [v3 08/12] x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry Chang S. Bae
2018-10-23 18:42 ` [v3 09/12] selftests/x86/fsgsbase: Test WRGSBASE Chang S. Bae
2018-10-23 18:42 ` [v3 10/12] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2018-10-23 18:42 ` [v3 11/12] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2018-10-23 18:42 ` [v3 12/12] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae

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=20181023184234.14025-1-chang.seok.bae@intel.com \
    --to=chang.seok.bae@intel.com \
    --cc=ak@linux.intel.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=markus.t.metzger@intel.com \
    --cc=mingo@kernel.org \
    --cc=ravi.v.shankar@intel.com \
    --cc=tglx@linutronix.de \
    /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

LKML Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
	git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
	git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
	git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
	git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
	git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
	git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
	git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
	git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
	git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
	git clone --mirror https://lore.kernel.org/lkml/10 lkml/git/10.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
		linux-kernel@vger.kernel.org
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git