From patchwork Mon Jun 29 13:29:26 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gleb Natapov X-Patchwork-Id: 32951 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n5TDU2uP005334 for ; Mon, 29 Jun 2009 13:30:03 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751226AbZF2N3c (ORCPT ); Mon, 29 Jun 2009 09:29:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758074AbZF2N3c (ORCPT ); Mon, 29 Jun 2009 09:29:32 -0400 Received: from mx2.redhat.com ([66.187.237.31]:57054 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751226AbZF2N3b (ORCPT ); Mon, 29 Jun 2009 09:29:31 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n5TDTUBB022703; Mon, 29 Jun 2009 09:29:30 -0400 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n5TDTT06031942; Mon, 29 Jun 2009 09:29:29 -0400 Received: from dhcp-1-237.tlv.redhat.com (dhcp-1-237.tlv.redhat.com [10.35.1.237]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id n5TDTRwR029410; Mon, 29 Jun 2009 09:29:27 -0400 Received: by dhcp-1-237.tlv.redhat.com (Postfix, from userid 13519) id 9E85518D479; Mon, 29 Jun 2009 16:29:26 +0300 (IDT) Date: Mon, 29 Jun 2009 16:29:26 +0300 From: Gleb Natapov To: "linux-kernel@vger.kernel.org" Cc: Suresh Siddha , Sheng Yang , "kvm@vger.kernel.org" , "avi@redhat.com" Subject: [PATCH v3] enable x2APIC without interrupt remapping under KVM Message-ID: <20090629132926.GB20289@redhat.com> MIME-Version: 1.0 Content-Disposition: inline X-Scanned-By: MIMEDefang 2.58 on 172.16.27.26 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org KVM would like to provide x2APIC interface to a guest without emulating interrupt remapping device. The reason KVM prefers guest to use x2APIC is that x2APIC interface is better virtualizable and provides better performance than mmio xAPIC interface: - msr exits are faster than mmio (no page table walk, emulation) - no need to read back ICR to look at the busy bit - one 64 bit ICR write instead of two 32 bit writes - shared code with the Hyper-V paravirt interface Included patch changes x2APIC enabling logic to enable it even if IR initialization failed, but kernel runs under KVM and no apic id is greater than 255 (if there is one spec requires BIOS to move to x2apic mode before starting an OS). Signed-off-by: Gleb Natapov --- v2: Add help message to Kconfig Force physical mode if IR is not available. v3: disable io-apic in outer function. Enable x2apic mode with masked io-apic -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index d1430ef..3e5b6ea 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -260,12 +260,15 @@ config SMP config X86_X2APIC bool "Support x2apic" - depends on X86_LOCAL_APIC && X86_64 && INTR_REMAP + depends on X86_LOCAL_APIC && X86_64 ---help--- This enables x2apic support on CPUs that have this feature. This allows 32-bit apic IDs (so it can support very large systems), - and accesses the local apic via MSRs not via mmio. + and accesses the local apic via MSRs not via mmio. CONFIG_INTR_REMAP + is required for x2apic to take affect when running on physical + machine. If you intend to run the kernel as KVM guest x2apic can + be used without interrupt remapping. If you don't know what to do here, say N. diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 8c7c042..f5f02c3 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -49,6 +49,7 @@ #include #include #include +#include unsigned int num_processors; @@ -1363,52 +1364,76 @@ void enable_x2apic(void) } #endif /* CONFIG_X86_X2APIC */ -void __init enable_IR_x2apic(void) +int __init enable_IR(void) { #ifdef CONFIG_INTR_REMAP int ret; - unsigned long flags; - struct IO_APIC_route_entry **ioapic_entries = NULL; ret = dmar_table_init(); if (ret) { pr_debug("dmar_table_init() failed with %d:\n", ret); - goto ir_failed; + return 0; } if (!intr_remapping_supported()) { pr_debug("intr-remapping not supported\n"); - goto ir_failed; + return 0; } - if (!x2apic_preenabled && skip_ioapic_setup) { pr_info("Skipped enabling intr-remap because of skipping " "io-apic setup\n"); - return; + return 0; } + if (enable_intr_remapping(x2apic_supported())) + return 0; + + pr_info("Enabled Interrupt-remapping\n"); + + return 1; + +#endif + return 0; +} + +void __init enable_IR_x2apic(void) +{ + unsigned long flags; + struct IO_APIC_route_entry **ioapic_entries = NULL; + int ret, x2apic_enabled = 0; + ioapic_entries = alloc_ioapic_entries(); if (!ioapic_entries) { - pr_info("Allocate ioapic_entries failed: %d\n", ret); - goto end; + pr_info("Allocate ioapic_entries failed\n"); + return; } ret = save_IO_APIC_setup(ioapic_entries); if (ret) { pr_info("Saving IO-APIC state failed: %d\n", ret); - goto end; + free_ioapic_entries(ioapic_entries); + return; } local_irq_save(flags); - mask_IO_APIC_setup(ioapic_entries); mask_8259A(); + mask_IO_APIC_setup(ioapic_entries); - ret = enable_intr_remapping(x2apic_supported()); - if (ret) - goto end_restore; + ret = enable_IR(); + if (!ret) { + /* IR is required if x2apic is enabled by BIOS even + * when running in kvm since this indicates present + * of APIC ID > 255 */ + if (x2apic_preenabled || !kvm_para_available()) + goto nox2apic; + else + /* without IR all CPUs can be addressed by IOAPIC/MSI + * only in physical mode */ + x2apic_phys = 1; + } - pr_info("Enabled Interrupt-remapping\n"); + x2apic_enabled = 1; if (x2apic_supported() && !x2apic_mode) { x2apic_mode = 1; @@ -1416,41 +1441,28 @@ void __init enable_IR_x2apic(void) pr_info("Enabled x2apic\n"); } -end_restore: - if (ret) - /* - * IR enabling failed - */ +nox2apic: + if (!ret) /* IR enabling failed */ restore_IO_APIC_setup(ioapic_entries); - unmask_8259A(); local_irq_restore(flags); -end: - if (ioapic_entries) - free_ioapic_entries(ioapic_entries); + free_ioapic_entries(ioapic_entries); - if (!ret) + if (x2apic_enabled) return; -ir_failed: - if (x2apic_preenabled) + if (x2apic_preenabled) { +#ifdef CONFIG_INTR_REMAP panic("x2apic enabled by bios. But IR enabling failed"); - else if (cpu_has_x2apic) - pr_info("Not enabling x2apic,Intr-remapping\n"); #else - if (!cpu_has_x2apic) - return; - - if (x2apic_preenabled) panic("x2apic enabled prior OS handover," - " enable CONFIG_X86_X2APIC, CONFIG_INTR_REMAP"); + " enable CONFIG_X86_X2APIC, CONFIG_INTR_REMAP"); #endif - - return; + } else if (cpu_has_x2apic) + pr_info("Not enabling x2apic,Intr-remapping\n"); } - #ifdef CONFIG_X86_64 /* * Detect and enable local APICs on non-SMP boards.