From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH] Replace kvm io delay pv-ops with linux magic Date: Fri, 20 Nov 2009 06:55:39 +0800 Message-ID: <4B05CCEB.5050802@goop.org> References: <1258548984-32433-1-git-send-email-agraf@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm list , Nick Piggin , Glauber Costa , Avi Kivity , virtualization@lists.linux-foundation.org To: Alexander Graf Return-path: Received: from claw.goop.org ([74.207.240.146]:33237 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756398AbZKSWzj (ORCPT ); Thu, 19 Nov 2009 17:55:39 -0500 In-Reply-To: <1258548984-32433-1-git-send-email-agraf@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: On 11/18/09 20:56, Alexander Graf wrote: > Currently we use pv-ops to tell linux not to do anything on io_delay. > > While the basic idea is good IMHO, I don't see why we would need pv-ops > for that. The io delay function already has a switch that can do nothing > if you're so inclined. > > So here's a patch (stacked on top of the previous pv-ops series) that > removes the io delay pv-ops hook and just sets the native io delay > variable instead. > Can you just get rid of the io_delay op altogether? If KVM doesn't need it, then nobody does. J > Signed-off-by: Alexander Graf > --- > arch/x86/Kconfig | 14 -------------- > arch/x86/kernel/kvm.c | 16 +++------------- > 2 files changed, 3 insertions(+), 27 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 97d4f92..ebed686 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -527,20 +527,6 @@ config KVM_GUEST > This option enables various optimizations for running under the KVM > hypervisor. > > -config KVM_IODELAY > - bool "KVM IO-delay support" > - depends on KVM_GUEST > - select PARAVIRT_CPU > - ---help--- > - Usually we wait for PIO access to complete. When inside KVM there's > - no need to do that, as we know that we're not going through a bus, > - but process PIO requests instantly. > - > - This option disables PIO waits, but drags in CPU-bound pv-ops. Thus > - you will probably get more speed loss than speedup using this option. > - > - If in doubt, say N. > - > config KVM_MMU > bool "KVM PV MMU support" > depends on KVM_GUEST > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index 7e0207f..be182e6 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -29,15 +29,6 @@ > #include > #include > > -#ifdef CONFIG_KVM_IODELAY > -/* > - * No need for any "IO delay" on KVM > - */ > -static void kvm_io_delay(void) > -{ > -} > -#endif /* CONFIG_KVM_IODELAY */ > - > #ifdef CONFIG_KVM_MMU > #define MMU_QUEUE_SIZE 1024 > > @@ -201,13 +192,12 @@ static void kvm_leave_lazy_mmu(void) > > static void __init paravirt_ops_setup(void) > { > + extern int io_delay_type; > pv_info.name = "KVM"; > pv_info.paravirt_enabled = 1; > > -#ifdef CONFIG_KVM_IODELAY > - if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY)) > - pv_cpu_ops.io_delay = kvm_io_delay; > -#endif > + /* Disable IO delay */ > + io_delay_type = CONFIG_IO_DELAY_TYPE_NONE; > > #ifdef CONFIG_KVM_MMU > if (kvm_para_has_feature(KVM_FEATURE_MMU_OP)) { >