Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753976Ab0ADWD4 (ORCPT ); Mon, 4 Jan 2010 17:03:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753715Ab0ADWDy (ORCPT ); Mon, 4 Jan 2010 17:03:54 -0500 Received: from hera.kernel.org ([140.211.167.34]:48112 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753011Ab0ADWDx (ORCPT ); Mon, 4 Jan 2010 17:03:53 -0500 Message-ID: <4B426550.6000209@kernel.org> Date: Mon, 04 Jan 2010 14:01:52 -0800 From: Yinghai Lu User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.5) Gecko/20091130 SUSE/3.0.0-1.1.1 Thunderbird/3.0 MIME-Version: 1.0 To: "H. Peter Anvin" CC: "Eric W. Biederman" , Jesse Brandeburg , Ingo Molnar , Thomas Gleixner , "linux-kernel@vger.kernel.org" , Andrew Morton , NetDEV list , Jesse Brandeburg , Suresh Siddha Subject: Re: Subject: [PATCH 1/2] x86: get back 15 vectors References: <4B347AEE.6030705@kernel.org> <20091228094707.GH24690@elte.hu> <4B398ECD.1080506@kernel.org> <4807377b1001031906s6b1ee576jc021da2642bb4147@mail.gmail.com> <4B415E73.1050801@kernel.org> <4B419113.1090204@kernel.org> <4B423B08.3010005@zytor.com> <4B424305.7050803@kernel.org> <4B4245FC.7070902@zytor.com> <4B424A5C.7080309@kernel.org> <4B425085.5040103@kernel.org> <4B42595E.9010404@zytor.com> <4B425BB7.90501@kernel.org> <4B425EB5.5080504@zytor.com> In-Reply-To: <4B425EB5.5080504@zytor.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3265 Lines: 85 On 01/04/2010 01:33 PM, H. Peter Anvin wrote: > On 01/04/2010 01:20 PM, Yinghai Lu wrote: >> --- linux-2.6.orig/arch/x86/include/asm/irq_vectors.h >> +++ linux-2.6/arch/x86/include/asm/irq_vectors.h >> @@ -30,8 +30,17 @@ >> /* >> * IDT vectors usable for external interrupt sources start >> * at 0x20: >> + * hpa said we can start from 0x1f. >> + * 0x1f is documented as reserved. However, the ability for the APIC >> + * to generate vectors starting at 0x10 is documented, as is the >> + * ability for the CPU to receive any vector number as an interrupt. >> + * 0x1f is used for IRQ_MOVE_CLEANUP_VECTOR since that vector needs >> + * an entire privilege level (16 vectors) all by itself at a higher >> + * priority than any actual device vector. Thus, by placing it in the >> + * otherwise-unusable 0x10 privilege level, we avoid wasting a full >> + * 16-vector block. >> */ >> -#define FIRST_EXTERNAL_VECTOR 0x20 >> +#define FIRST_EXTERNAL_VECTOR 0x1f >> >> #ifdef CONFIG_X86_32 >> # define SYSCALL_VECTOR 0x80 >> @@ -41,15 +50,19 @@ >> #endif >> >> /* >> - * Reserve the lowest usable priority level 0x20 - 0x2f for triggering >> + * Reserve the lowest usable priority level 0x10 - 0x1f for triggering >> * cleanup after irq migration. >> + * this overlaps with the reserved range for cpu exceptions so this >> + * will need to be changed to 0x20 - 0x2f if the last cpu exception is >> + * ever allocated. >> */ >> + >> #define IRQ_MOVE_CLEANUP_VECTOR FIRST_EXTERNAL_VECTOR >> >> /* >> - * Vectors 0x30-0x3f are used for ISA interrupts. >> + * Vectors 0x20-0x2f are used for ISA interrupts. >> */ >> -#define IRQ0_VECTOR (FIRST_EXTERNAL_VECTOR + 0x10) >> +#define IRQ0_VECTOR (FIRST_EXTERNAL_VECTOR + 1) >> >> #define IRQ1_VECTOR (IRQ0_VECTOR + 1) >> #define IRQ2_VECTOR (IRQ0_VECTOR + 2) >> @@ -68,6 +81,13 @@ >> #define IRQ15_VECTOR (IRQ0_VECTOR + 15) >> > > I'm not sure that making IRQ_MOVE_CLEANUP_VECTOR and IRQ0_VECTOR offsets > from FIRST_EXTERNAL_VECTOR makes sense from a readability perspective. > These are now magic numbers, and making them offsets is only confusing, > as it implies we could do it differently. > > If nothing else, the actual logic for IRQ0_VECTOR should be: > > #define IRQ0_VECTOR ((FIRST_EXTERNAL_VECTOR + 16) & ~15) > > ... since that is what we actually want -- we round up to the next > 16-vector boundary. Both +16 and +1 misrepresent the logic. that will be good, if later update FIRST_EXTERNAL_VECTOR... > >> /* >> + * First APIC vector available to drivers: (vectors 0x30-0xee) we >> + * start at 0x31 to spread out vectors evenly between priority >> + * levels. (0x80 is the syscall vector) >> + */ >> +#define FIRST_DEVICE_VECTOR (IRQ15_VECTOR + 2) >> + > > We really should fix that so we can do +1 here instead of +2; that > presumably means fixing the logic so we do something smarter than just > jump over 0x80. we already use used_vectors to skip 0x80. so we could change that to +1? YH -- 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/