linux-kernel - Re: [PATCH v3 0/2] guard virt_spin

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Message-ID: <20171002141911.ucl4c73ztqt54hby@hirez.programming.kicks-ass.net>
Date:   Mon, 2 Oct 2017 16:19:11 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org, virtualization@...ts.linux-foundation.org,
        jeremy@...p.org, chrisw@...s-sol.org, akataria@...are.com,
        rusty@...tcorp.com.au, boris.ostrovsky@...cle.com, hpa@...or.com,
        tglx@...utronix.de, mingo@...hat.com, longman@...hat.com
Subject: Re: [PATCH v3 0/2] guard virt_spin_lock() with a static key

On Wed, Sep 06, 2017 at 07:36:23PM +0200, Juergen Gross wrote:
> With virt_spin_lock() being guarded by a static key the bare metal case
> can be optimized by patching the call away completely. In case a kernel
> running as a guest it can decide whether to use paravitualized
> spinlocks, the current fallback to the unfair test-and-set scheme, or
> to mimic the bare metal behavior.
> 
> V3:
> - remove test for hypervisor environment from virt_spin_lock(9 as
>   suggested by Waiman Long
> 
> V2:
> - use static key instead of making virt_spin_lock() a pvops function
> 
> Juergen Gross (2):
>   paravirt/locks: use new static key for controlling call of
>     virt_spin_lock()
>   paravirt,xen: correct xen_nopvspin case
> 
>  arch/x86/include/asm/qspinlock.h     | 11 ++++++++++-
>  arch/x86/kernel/paravirt-spinlocks.c |  6 ++++++
>  arch/x86/kernel/smpboot.c            |  2 ++
>  arch/x86/xen/spinlock.c              |  2 ++
>  kernel/locking/qspinlock.c           |  4 ++++
>  5 files changed, 24 insertions(+), 1 deletion(-)

Sorry for the delay, picked it up now.