linux-kernel - Re: [PATCH v2 0/2] x86/entry: speed up context-tracking system calls by 150 clock cycles

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Date:	Tue, 21 Jun 2016 15:24:07 +0200
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc:	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 0/2] x86/entry: speed up context-tracking system calls
 by 150 clock cycles

On 06/20/2016 04:58 PM, Paolo Bonzini wrote:
> The first patches are the two optimizations I posted on May 30th
> for the system call entry/exit code.  The only change is in the
> function names, which use the user_{enter,exit}_irqoff favored
> by Andy and Ingo.  The first patch matches what commit d0e536d8939
> ("context_tracking: avoid irq_save/irq_restore on guest entry and exit",
> 2015-10-28) did for guest entry and exit.  The second simply adds
> an inline annotation; the compiler doesn't figure it out because the
> function is not static.
> 
> The second two patches move guest_{enter,exit} to the same naming
> convention, removing the KVM wrappers kvm_guest_{enter,exit} and
> __kvm_guest_{enter,exit} in the process.  I would like these two to
> go through the KVM tree because I have other optimizations for 4.8
> on top of these patches.
> 
> Thanks,
> 
> Paolo
> 
> Paolo Bonzini (4):
>   x86/entry: Avoid interrupt flag save and restore
>   x86/entry: Inline enter_from_user_mode
>   context_tracking: move rcu_virt_note_context_switch out of kvm_host.h
>   KVM: remove kvm_guest_enter/exit wrappers
> 
>  arch/arm/kvm/arm.c               |  8 +++---
>  arch/mips/kvm/mips.c             |  4 +--
>  arch/powerpc/kvm/book3s_hv.c     |  4 +--
>  arch/powerpc/kvm/book3s_pr.c     |  4 +--
>  arch/powerpc/kvm/booke.c         |  4 +--
>  arch/powerpc/kvm/powerpc.c       |  2 +-
>  arch/s390/kvm/kvm-s390.c         |  4 +--
>  arch/x86/entry/common.c          |  6 ++---
>  arch/x86/kvm/x86.c               |  4 +--
>  include/linux/context_tracking.h | 53 +++++++++++++++++++++++++++++++++++++---
>  include/linux/kvm_host.h         | 39 -----------------------------
>  11 files changed, 69 insertions(+), 63 deletions(-)
> 
Series looks sane and does work on s390.
It has a minor conflict with my vsie pull request (so either add vsie.c
to this patch set or fixup my pull request in the merge commit to replace
kvm_guest_exit/enter with the new functions.

Christian