L!TF Bulletin #6: The vacation brain edition

L!TF Bulletin #6: The vacation brain edition

[Thomas Gleixner]

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Hi!

I'm going to take a one week break to regain some mental sanity as I'm
running on emergency fuel way too long already.

The current state of affairs is attached as git bundle, which would be the
pile to pull from in case the embargo breaks unexpectedly next week. The
stable branches (4.17,16,14) in the sekrit repository contain the same pile
of changes.

The bundle contains:

  - Host side L1TF mitigation: Page Table Inversion for non present PTEs on
    all levels. This makes sure that non-present PTEs point to non-existing
    or non-cachable areas.

  - A sysfs interface for exposing the L1TF mitigation state of the kernel
    including VMX.

  - A sysfs interface to control and query SMT state. Allows to offline all
    "secondary" hyperthreads so that only one thread per physical core
    stays online. Turning it back on, re-onlines the offline hyper threads
    again.

  - Command line interface for controlling SMT state at boot time.

  - VMX support for fluhsing L1D before VMENTER either via a software
    algorithm or via the new MSR if updated microcode provides it.

  - Command line/module parameter to control L1D flush before VMENTER at
    module init and at run time.

  - Command line option to select the mitigation state for VMX via
    combinations of L1D flush methods and SMT control.

  - Comprehensive documentation of the issue, affected processors,
    mitigation methods, their limitations and the control interfaces.

What's outstanding at moment are the optimizations for nested VMs, but as
these are optimizations they are not super urgent right now. Let's hope
everything works out according to embargo plan, so we have enough time to
hash out the extra bells and whistles.

Aside of that the promised 4.9 backport has not materialized yet, but
that's the least of _my_ worries as I'm not a member of the kernel
necrophilia cult.

If urgent fixes need to be applied, Peter Zijlstra and Ingo Molnar have
write access to the repository.

If there are any issues with the mailing list(s), please contact:

     Anna-Maria Gleixner <anna-maria@linutronix.de>
and
     Sebastian Siewior <bigeasy@linutronix.de>

They can add/change subscribers as well.

Talk to you soon again!

Thanks,

	Thomas

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[MODERATED] Re: L!TF Bulletin #6: The vacation brain edition

[Konrad Rzeszutek Wilk]

On Fri, Jul 20, 2018 at 10:47:14PM +0200, speck for Thomas Gleixner wrote:
> Hi!
> 
> I'm going to take a one week break to regain some mental sanity as I'm
> running on emergency fuel way too long already.

Enjoy your vacation! Thank you for leading these efforts and banging these
patchsets together so that we have everything ready!