[src/trunk]: src/sys/arch/x86/x86 Add TODO comments to support MSI multiple v...

[knakahara <knakahara%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9ea505eaa8cc
branches:  trunk
changeset: 451804:9ea505eaa8cc
user:      knakahara <knakahara%NetBSD.org@localhost>
date:      Wed Jun 05 04:31:37 2019 +0000

description:
Add TODO comments to support MSI multiple vectors on x86 systems.

diffstat:

 sys/arch/x86/x86/intr.c |  17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diffs (38 lines):

diff -r 01f19bd6621d -r 9ea505eaa8cc sys/arch/x86/x86/intr.c
--- a/sys/arch/x86/x86/intr.c   Wed Jun 05 03:49:07 2019 +0000
+++ b/sys/arch/x86/x86/intr.c   Wed Jun 05 04:31:37 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: intr.c,v 1.144 2019/02/15 08:54:01 nonaka Exp $        */
+/*     $NetBSD: intr.c,v 1.145 2019/06/05 04:31:37 knakahara Exp $     */
 
 /*
  * Copyright (c) 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -133,7 +133,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: intr.c,v 1.144 2019/02/15 08:54:01 nonaka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: intr.c,v 1.145 2019/06/05 04:31:37 knakahara Exp $");
 
 #include "opt_intrdebug.h"
 #include "opt_multiprocessor.h"
@@ -661,6 +661,19 @@
        if (pic == &i8259_pic) {
                idtvec = ICU_OFFSET + pin;
        } else {
+               /*
+                * TODO to support MSI (not MSI-X) multiple vectors
+                *
+                * PCI Local Bus Specification Revision 3.0 says the devices
+                * which use MSI multiple vectors increment the low order bits
+                * of MSI message data.
+                * On the other hand, Intel SDM "10.11.2 Message Data Register
+                * Format" says the 7:0 bits of MSI message data mean Interrupt
+                * Descriptor Table(IDT) vector.
+                * As the result of these two documents, the IDT vectors which
+                * are used by a device using MSI multiple vectors must be
+                * continuous.
+                */
                idtvec = idt_vec_alloc(APIC_LEVEL(level), IDT_INTR_HIGH);
        }
        if (idtvec == 0) {