Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752695Ab2FROvB (ORCPT ); Mon, 18 Jun 2012 10:51:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12930 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751999Ab2FROvA (ORCPT ); Mon, 18 Jun 2012 10:51:00 -0400 Date: Mon, 18 Jun 2012 17:50:41 +0300 From: "Michael S. Tsirkin" To: Avi Kivity Cc: x86@kernel.org, kvm@vger.kernel.org, Ingo Molnar , "H. Peter Anvin" , Marcelo Tosatti , gleb@redhat.com, Linus Torvalds , linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCHv7 3/8] kvm_para: guest side for eoi avoidance Message-ID: <20120618145041.GE26540@redhat.com> References: <4c5bedc5cb55dcea1676b913a0f6da3f04b03145.1339681762.git.mst@redhat.com> <4FDF3874.2050208@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FDF3874.2050208@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3170 Lines: 95 On Mon, Jun 18, 2012 at 05:17:24PM +0300, Avi Kivity wrote: > On 06/14/2012 04:53 PM, Michael S. Tsirkin wrote: > > The idea is simple: there's a bit, per APIC, in guest memory, > > that tells the guest that it does not need EOI. > > Guest tests it using a single est and clear operation - this is > > necessary so that host can detect interrupt nesting - and if set, it can > > skip the EOI MSR. > > > > I run a simple microbenchmark to show exit reduction > > (note: for testing, need to apply follow-up patch > > 'kvm: host side for eoi optimization' + a qemu patch > > I posted separately, on host): > > > > > > diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h > > index a6983b2..47f9eff 100644 > > --- a/arch/x86/include/asm/bitops.h > > +++ b/arch/x86/include/asm/bitops.h > > @@ -28,11 +28,13 @@ > > #if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1) > > /* Technically wrong, but this avoids compilation errors on some gcc > > versions. */ > > -#define BITOP_ADDR(x) "=m" (*(volatile long *) (x)) > > +#define BITOP_ADDR_CONSTRAINT "=m" > > #else > > -#define BITOP_ADDR(x) "+m" (*(volatile long *) (x)) > > +#define BITOP_ADDR_CONSTRAINT "+m" > > #endif > > > > +#define BITOP_ADDR(x) BITOP_ADDR_CONSTRAINT (*(volatile long *) (x)) > > + > > #define ADDR BITOP_ADDR(addr) > > What's this doing here? Ugh. More leftovers from when I had inline asm here. Will remove. > > > > +/* size alignment is implied but just to make it explicit. */ > > +static DEFINE_PER_CPU(unsigned long, kvm_apic_eoi) __aligned(2) = > > + KVM_PV_EOI_DISABLED; > > You're actually breaking the alignment. ulong has 8 byte alignment > sometimes and you can make it cross cache boundary this way. No, if you look at the definition of __aligned you will see that it limits the alignment from below. Compiler still applies the natural size alignment. You are not the first to get confused. So I wonder: is it better to add a comment or simply remove __aligned here. > > + > > void __cpuinit kvm_guest_cpu_init(void) > > { > > if (!kvm_para_available()) > > @@ -300,11 +320,17 @@ void __cpuinit kvm_guest_cpu_init(void) > > smp_processor_id()); > > } > > > > + if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) { > > + __get_cpu_var(kvm_apic_eoi) = 0; > > + wrmsrl(MSR_KVM_PV_EOI_EN, __pa(&__get_cpu_var(kvm_apic_eoi)) | > > + KVM_MSR_ENABLED); > > Bad formatting. I guess temporary will make it prettier. unsigned long pa; __get_cpu_var(kvm_apic_eoi) = 0; pa = __pa(&__get_cpu_var(kvm_apic_eoi)) | KVM_MSR_ENABLED; wrmsrl(MSR_KVM_PV_EOI_EN, pa); or did I miss the point? > > + } > > + > > if (has_steal_clock) > > kvm_register_steal_time(); > > } > > > > > Please check that the kexec path also disables pveoi. The chunk in kvm_pv_guest_cpu_reboot does this, doesn't it? > -- > error compiling committee.c: too many arguments to function > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/