Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754517Ab0LGB7P (ORCPT ); Mon, 6 Dec 2010 20:59:15 -0500 Received: from mga02.intel.com ([134.134.136.20]:28657 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753658Ab0LGB7O (ORCPT ); Mon, 6 Dec 2010 20:59:14 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.59,308,1288594800"; d="scan'208";a="581194990" From: Sheng Yang Organization: Intel Opensource Technology Center To: Jeremy Fitzhardinge Subject: Re: [PATCH v2] xen: HVM X2APIC support Date: Tue, 7 Dec 2010 10:01:48 +0800 User-Agent: KMail/1.13.5 (Linux/2.6.35-22-generic; KDE/4.5.1; x86_64; ; ) Cc: Stefano Stabellini , linux-kernel@vger.kernel.org, "xen-devel@lists.xensource.com" References: <1291621797-1483-1-git-send-email-sheng@linux.intel.com> <4CFD265B.1000504@goop.org> In-Reply-To: <4CFD265B.1000504@goop.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <201012071001.49039.sheng@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5399 Lines: 184 On Tuesday 07 December 2010 02:07:23 Jeremy Fitzhardinge wrote: > On 12/05/2010 11:49 PM, Sheng Yang wrote: > > This patch is similiar to Gleb Natapov's patch for KVM, which enable the > > hypervisor to emulate x2apic feature for the guest. By this way, the > > emulation of lapic would be simpler with x2apic interface(MSR), and > > faster. > > > > Signed-off-by: Sheng Yang > > --- > > > > arch/x86/include/asm/xen/hypervisor.h | 35 > > +++++++++++++++++++++++++++++++++ arch/x86/kernel/apic/apic.c > > | 4 ++- > > arch/x86/xen/enlighten.c | 30 ++++++++++----------------- > > 3 files changed, 49 insertions(+), 20 deletions(-) > > > > diff --git a/arch/x86/include/asm/xen/hypervisor.h > > b/arch/x86/include/asm/xen/hypervisor.h index 396ff4c..bc5b804 100644 > > --- a/arch/x86/include/asm/xen/hypervisor.h > > +++ b/arch/x86/include/asm/xen/hypervisor.h > > @@ -37,4 +37,39 @@ > > > > extern struct shared_info *HYPERVISOR_shared_info; > > extern struct start_info *xen_start_info; > > > > +#include > > + > > +static inline uint32_t xen_cpuid_base(void) > > +{ > > + uint32_t base, eax, ebx, ecx, edx; > > + char signature[13]; > > + > > + for (base = 0x40000000; base < 0x40010000; base += 0x100) { > > + cpuid(base, &eax, &ebx, &ecx, &edx); > > + *(uint32_t *)(signature + 0) = ebx; > > + *(uint32_t *)(signature + 4) = ecx; > > + *(uint32_t *)(signature + 8) = edx; > > + signature[12] = 0; > > + > > + if (!strcmp("XenVMMXenVMM", signature) && ((eax - base) >= 2)) > > + return base; > > + } > > + > > + return 0; > > +} > > + > > +#ifdef CONFIG_XEN > > +extern bool xen_hvm_need_lapic(void); > > + > > +static inline bool xen_para_available(void) > > +{ > > + return xen_hvm_need_lapic(); > > +} > > +#else > > +static inline bool xen_para_available(void) > > +{ > > + return (xen_cpuid_base() != 0); > > +} > > +#endif > > Surely this should be using the asm/hypervisor.h interface? I think it's the proper place. Or any suggestion? > > > + > > > > #endif /* _ASM_X86_XEN_HYPERVISOR_H */ > > > > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > > index 3f838d5..1b68221 100644 > > --- a/arch/x86/kernel/apic/apic.c > > +++ b/arch/x86/kernel/apic/apic.c > > @@ -52,6 +52,7 @@ > > > > #include > > #include > > #include > > > > +#include > > > > unsigned int num_processors; > > > > @@ -1476,7 +1477,8 @@ void __init enable_IR_x2apic(void) > > > > /* IR is required if there is APIC ID > 255 even when running > > > > * under KVM > > */ > > > > - if (max_physical_apicid > 255 || !kvm_para_available()) > > + if (max_physical_apicid > 255 || > > + (!kvm_para_available() && !xen_para_available())) > > > > goto nox2apic; > > What are the downsides of just using x2apic unconditionally? > > Assuming there is some downside to using it all the time, what about > adding a pseudo-cpu feature flag meaning "use x2apic unconditionally" > rather than adding a bunch of ad-hoc tests here? Because for native, x2apic should be used with interrupt-remapping, otherwise it didn't make much sense for native(the main reason to x2apic for bare-metal is support big machine with more than 255 APIC-ID, and without interrupt remapping it can't do so). But for hypervisor, we want to emulate the accessing faster through MSR, so we want them. > > > /* > > > > * without IR all CPUs can be addressed by IOAPIC/MSI > > > > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c > > index 235c0f4..7ef1645 100644 > > --- a/arch/x86/xen/enlighten.c > > +++ b/arch/x86/xen/enlighten.c > > @@ -1245,25 +1245,6 @@ asmlinkage void __init xen_start_kernel(void) > > > > #endif > > } > > > > -static uint32_t xen_cpuid_base(void) > > -{ > > - uint32_t base, eax, ebx, ecx, edx; > > - char signature[13]; > > - > > - for (base = 0x40000000; base < 0x40010000; base += 0x100) { > > - cpuid(base, &eax, &ebx, &ecx, &edx); > > - *(uint32_t *)(signature + 0) = ebx; > > - *(uint32_t *)(signature + 4) = ecx; > > - *(uint32_t *)(signature + 8) = edx; > > - signature[12] = 0; > > - > > - if (!strcmp("XenVMMXenVMM", signature) && ((eax - base) >= 2)) > > - return base; > > - } > > - > > - return 0; > > -} > > - > > > > static int init_hvm_pv_info(int *major, int *minor) > > { > > > > uint32_t eax, ebx, ecx, edx, pages, msr, base; > > > > @@ -1373,6 +1354,17 @@ static bool __init xen_hvm_platform(void) > > > > return true; > > > > } > > > > +bool xen_hvm_need_lapic(void) > > Where does this get used? ?... xen_para_available() above... -- regards Yang, Sheng > > > +{ > > + if (xen_pv_domain()) > > + return false; > > + if (xen_hvm_domain() && > > + (xen_feature(XENFEAT_hvm_pirqs) || xen_have_vector_callback)) > > + return false; > > + return (xen_cpuid_base() != 0); > > +} > > +EXPORT_SYMBOL_GPL(xen_hvm_need_lapic); > > + > > > > const __refconst struct hypervisor_x86 x86_hyper_xen_hvm = { > > > > .name = "Xen HVM", > > .detect = xen_hvm_platform, > > J -- 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/