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From: "Bae, Chang Seok" <chang.seok.bae@intel.com>
To: Sasha Levin <sashal@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Andi Kleen <ak@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	"Metzger, Markus T" <markus.t.metzger@intel.com>,
	"hpa@zytor.com" <hpa@zytor.com>, "bp@alien8.de" <bp@alien8.de>,
	"Hansen, Dave" <dave.hansen@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>,
	Pedro Alves <palves@redhat.com>, Simon Marchi <simark@simark.ca>,
	"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v9 00/17] Enable FSGSBASE instructions
Date: Tue, 21 Apr 2020 17:15:34 +0000	[thread overview]
Message-ID: <4764C01A-D225-46FF-A9AF-BAA9CD3EB41C@intel.com> (raw)
In-Reply-To: <20200421160622.GJ1809@sasha-vm>


> On Apr 21, 2020, at 09:06, Sasha Levin <sashal@kernel.org> wrote:
> 
> Andi's point is that there is no known user it breaks, and the Intel
> folks did some digging into potential users who might be affected by
> this, including 'rr' brought up by Andy, and concluded that there won't
> be breakage as a result of this patchset:

FWIW, we surveyed tools like rr and CRIU before. Their comments are [*,**]:

   "Anyway I think rr will be fine with the new behavior. Our modifications
    to fs/gs/fs_base/gs_base are always either a) setting values that the
    kernel set during recording to make them happen during replay or b)
    emulating PTRACE_SET_REGS that a tracee ptracer tried to set on another
    tracee. Either way I think the effects are going to be the same as what
    would happen if the program were run without rr.”

   "Internally in criu we fetch the regset via ptrace and keep them in
    images as they were at moment of dump (if ldt is being used we don't
    support such tasks) so I think the changes should not break criu."

What we took away was that those tools reactively follow the underlying
kernel's behavior; so, they should be fine with the FSGSBASE-brought new
behaviors.

[*] https://mail.mozilla.org/pipermail/rr-dev/2018-March/000615.html
[**] https://lists.openvz.org/pipermail/criu/2018-March/040654.html

Thanks,
Chang

  parent reply	other threads:[~2020-04-21 17:15 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04 18:15 [PATCH v9 00/17] Enable FSGSBASE instructions Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 01/17] x86/ptrace: Prevent ptrace from clearing the FS/GS selector Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 02/17] selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 03/17] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 04/17] x86/entry/64: Clean up paranoid exit Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 05/17] x86/entry/64: Switch CR3 before SWAPGS in paranoid entry Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 06/17] x86/entry/64: Introduce the FIND_PERCPU_BASE macro Chang S. Bae
2019-10-04 18:15 ` [PATCH v9 07/17] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 08/17] x86/entry/64: Document GSBASE handling in the paranoid path Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 09/17] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 10/17] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 11/17] x86/fsgsbase/64: Use FSGSBASE in switch_to() if available Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 12/17] x86/fsgsbase/64: Use FSGSBASE instructions on thread copy and ptrace Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 13/17] x86/speculation/swapgs: Check FSGSBASE in enabling SWAPGS mitigation Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 14/17] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 15/17] x86/fsgsbase/64: Enable FSGSBASE on 64bit by default and add a chicken bit Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 16/17] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2019-10-04 18:16 ` [PATCH v9 17/17] Documentation/x86/64: Add documentation for GS/FS addressing mode Chang S. Bae
2019-10-04 22:54   ` Randy Dunlap
2019-11-15 18:29 ` [PATCH v9 00/17] Enable FSGSBASE instructions Thomas Gleixner
2019-11-15 19:12   ` Andi Kleen
2019-11-29 14:56     ` Metzger, Markus T
2019-11-29 16:51       ` Andy Lutomirski
2019-12-02  8:23         ` Metzger, Markus T
2019-12-04 20:20           ` Andy Lutomirski
2019-12-10  8:27             ` Metzger, Markus T
2020-02-24 18:02             ` Bae, Chang Seok
2020-04-13 20:03               ` Sasha Levin
2020-04-14  0:32                 ` Andi Kleen
2020-04-17 13:30                   ` Sasha Levin
2020-04-17 15:52                     ` Andy Lutomirski
2020-04-20 14:13                       ` Andi Kleen
2020-04-20 17:14                         ` Thomas Gleixner
2020-04-21 16:06                           ` Sasha Levin
2020-04-21 16:49                             ` Andy Lutomirski
2020-04-21 20:02                               ` Andi Kleen
2020-04-21 17:15                             ` Bae, Chang Seok [this message]
2020-04-21 19:56                             ` Andi Kleen
2020-04-21 20:21                               ` Andy Lutomirski
2020-04-21 20:51                                 ` Sasha Levin
2020-04-22 23:00                                   ` Andy Lutomirski
2020-04-23  4:08                                     ` Sasha Levin
2020-04-25 22:39                                       ` Thomas Gleixner
2020-04-26  2:52                                         ` Sasha Levin
2020-04-26 10:04                                           ` Thomas Gleixner
2020-04-14 15:47                 ` Bae, Chang Seok

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