From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758186Ab3CDPOE (ORCPT ); Mon, 4 Mar 2013 10:14:04 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:37582 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757838Ab3CDPOD (ORCPT ); Mon, 4 Mar 2013 10:14:03 -0500 Date: Mon, 4 Mar 2013 10:13:28 -0500 From: Konrad Rzeszutek Wilk To: Boris Ostrovsky Cc: hpa@zytor.com, bp@alien8.de, mingo@redhat.com, tglx@linutronix.de, rostedt@goodmis.org, gregkh@linuxfoundation.org, samu.kallio@aberdeencloud.com, kraman@redhat.com, jwboyer@redhat.com, xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: [PATCH] mm/x86: Patch out arch_flush_lazy_mmu_mode() when running on bare metal Message-ID: <20130304151328.GA16634@phenom.dumpdata.com> References: <1362092149-32381-1-git-send-email-boris.ostrovsky@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1362092149-32381-1-git-send-email-boris.ostrovsky@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 28, 2013 at 05:55:49PM -0500, Boris Ostrovsky wrote: > Invoking arch_flush_lazy_mmu_mode() results in calls to > preempt_enable()/disable() which may have performance impact. > > Since lazy MMU is not used on bare metal we can patch away > arch_flush_lazy_mmu_mode() so that it is never called in such > environment. > > Signed-off-by: Boris Ostrovsky I am OK with this - had also run it overnight on baremetal/xen to make sure there were no funny business. > --- > arch/x86/include/asm/paravirt.h | 5 ++++- > arch/x86/include/asm/paravirt_types.h | 2 ++ > arch/x86/kernel/paravirt.c | 25 +++++++++++++------------ > arch/x86/lguest/boot.c | 1 + > arch/x86/xen/mmu.c | 1 + > 5 files changed, 21 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h > index 5edd174..7361e47 100644 > --- a/arch/x86/include/asm/paravirt.h > +++ b/arch/x86/include/asm/paravirt.h > @@ -703,7 +703,10 @@ static inline void arch_leave_lazy_mmu_mode(void) > PVOP_VCALL0(pv_mmu_ops.lazy_mode.leave); > } > > -void arch_flush_lazy_mmu_mode(void); > +static inline void arch_flush_lazy_mmu_mode(void) > +{ > + PVOP_VCALL0(pv_mmu_ops.lazy_mode.flush); > +} > > static inline void __set_fixmap(unsigned /* enum fixed_addresses */ idx, > phys_addr_t phys, pgprot_t flags) > diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h > index 142236e..b3b0ec1 100644 > --- a/arch/x86/include/asm/paravirt_types.h > +++ b/arch/x86/include/asm/paravirt_types.h > @@ -91,6 +91,7 @@ struct pv_lazy_ops { > /* Set deferred update mode, used for batching operations. */ > void (*enter)(void); > void (*leave)(void); > + void (*flush)(void); > }; > > struct pv_time_ops { > @@ -679,6 +680,7 @@ void paravirt_end_context_switch(struct task_struct *next); > > void paravirt_enter_lazy_mmu(void); > void paravirt_leave_lazy_mmu(void); > +void paravirt_flush_lazy_mmu(void); > > void _paravirt_nop(void); > u32 _paravirt_ident_32(u32); > diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c > index 17fff18..8bfb335 100644 > --- a/arch/x86/kernel/paravirt.c > +++ b/arch/x86/kernel/paravirt.c > @@ -263,6 +263,18 @@ void paravirt_leave_lazy_mmu(void) > leave_lazy(PARAVIRT_LAZY_MMU); > } > > +void paravirt_flush_lazy_mmu(void) > +{ > + preempt_disable(); > + > + if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) { > + arch_leave_lazy_mmu_mode(); > + arch_enter_lazy_mmu_mode(); > + } > + > + preempt_enable(); > +} > + > void paravirt_start_context_switch(struct task_struct *prev) > { > BUG_ON(preemptible()); > @@ -292,18 +304,6 @@ enum paravirt_lazy_mode paravirt_get_lazy_mode(void) > return this_cpu_read(paravirt_lazy_mode); > } > > -void arch_flush_lazy_mmu_mode(void) > -{ > - preempt_disable(); > - > - if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) { > - arch_leave_lazy_mmu_mode(); > - arch_enter_lazy_mmu_mode(); > - } > - > - preempt_enable(); > -} > - > struct pv_info pv_info = { > .name = "bare hardware", > .paravirt_enabled = 0, > @@ -475,6 +475,7 @@ struct pv_mmu_ops pv_mmu_ops = { > .lazy_mode = { > .enter = paravirt_nop, > .leave = paravirt_nop, > + .flush = paravirt_nop, > }, > > .set_fixmap = native_set_fixmap, > diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c > index 1cbd89c..7114c63 100644 > --- a/arch/x86/lguest/boot.c > +++ b/arch/x86/lguest/boot.c > @@ -1334,6 +1334,7 @@ __init void lguest_init(void) > pv_mmu_ops.read_cr3 = lguest_read_cr3; > pv_mmu_ops.lazy_mode.enter = paravirt_enter_lazy_mmu; > pv_mmu_ops.lazy_mode.leave = lguest_leave_lazy_mmu_mode; > + pv_mmu_ops.lazy_mode.flush = paravirt_flush_lazy_mmu; > pv_mmu_ops.pte_update = lguest_pte_update; > pv_mmu_ops.pte_update_defer = lguest_pte_update; > > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c > index e8e3493..f4f4105 100644 > --- a/arch/x86/xen/mmu.c > +++ b/arch/x86/xen/mmu.c > @@ -2197,6 +2197,7 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = { > .lazy_mode = { > .enter = paravirt_enter_lazy_mmu, > .leave = xen_leave_lazy_mmu, > + .flush = paravirt_flush_lazy_mmu, > }, > > .set_fixmap = xen_set_fixmap, > -- > 1.8.1.2 >