From: Neil Horman <nhorman@redhat.com>
Date: Wed, 27 May 2009 20:48:02 -0400
Subject: [x86] fix mcp55 apic routing
Message-id: 20090528004802.GD19076@localhost.localdomain
O-Subject: [RHEL 5.5 PATCH] i386: fix mcp55 apic routing (bz 473404)
Bugzilla: 473404
RH-Acked-by: Stefan Assmann <sassmann@redhat.com>
RH-Acked-by: Ivan Vecera <ivecera@redhat.com>
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>

A few days ago, I posted a bug fix for apic interrupt routing using mcp55, and
it was astutely pointed out that I probably need the same fix for x86 (since the
prior pach was for x86_64).  This patch applies on top of the former patch and
fixes the use of mcp55 with kdump on x86 code.  Verified by me.  Fixes bz 473404

Neil

diff --git a/arch/i386/kernel/crash.c b/arch/i386/kernel/crash.c
index 26554bf..a203412 100644
--- a/arch/i386/kernel/crash.c
+++ b/arch/i386/kernel/crash.c
@@ -24,6 +24,7 @@
 #include <asm/apic.h>
 #include <mach_ipi.h>
 #include <linux/kvm_para.h>
+#include <linux/pci.h>
 
 
 /* This keeps a track of which one is crashing cpu. */
@@ -158,6 +159,8 @@ static void nmi_shootdown_cpus(void)
 #endif
 #endif /* CONFIG_XEN */
 
+extern struct pci_dev *mcp55_rewrite;
+
 void machine_crash_shutdown(struct pt_regs *regs)
 {
 #ifndef CONFIG_XEN
@@ -182,6 +185,25 @@ void machine_crash_shutdown(struct pt_regs *regs)
 #if defined(CONFIG_X86_IO_APIC)
 	disable_IO_APIC();
 #endif
+	if (crashing_cpu && mcp55_rewrite) {
+		u32 cfg;
+		printk(KERN_CRIT "REWRITING MCP55 CFG REG\n");
+		/*
+		 * We have a mcp55 chip on board which has been 
+		 * flagged as only sending legacy interrupts
+		 * to the BSP, and we are crashing on an AP
+		 * This is obviously bad, and we need to 
+		 * fix it up.  To do this we write to the 
+		 * flagged device, to the register at offset 0x74
+		 * and we make sure that bit 2 and bit 15 are clear
+		 * This forces legacy interrupts to be broadcast
+		 * to all cpus
+		 */
+		pci_read_config_dword(mcp55_rewrite, 0x74, &cfg);
+		cfg &= ~((1 << 2) | (1 << 15));
+		printk(KERN_CRIT "CFG = %x\n", cfg);
+		pci_write_config_dword(mcp55_rewrite, 0x74, cfg);
+	}
 #endif /* CONFIG_XEN */
 	crash_save_self(regs);
 }