From: Prarit Bhargava <prarit@redhat.com>
Date: Fri, 14 Sep 2007 09:07:54 -0400
Subject: [x86_64] kdump: shutdown gart on k8 systems
Message-id: 20070914130754.28966.43946.sendpatchset@prarit.boston.redhat.com
O-Subject: [RHEL 5.2 PATCH]: Fix kexec/kdump on systems with gart & >4G mem
Bugzilla: 264601

Backport of git commit bc2cea6a34fdb30f118ec75db39a46a191870607.

For K8 system: 4G RAM with memory hole remapping enabled, or more than 4G RAM
installed. when using kexec to load second kernel. In the second kernel,
when mem is allocated for GART, it will do the memset for clear, it will cause
restart, because some device still used that for dma.
solution will be:
in second kernel: disable that at first before we try to allocate mem for it.
or in the first kernel: do disable that before shutdown.
Andi/Eric/Alan prefer to second one for clean shutdown in first kernel.
Andi also point out need to consider to AGP enable but mem less 4G case too.

Compile & boot tested on a non-effected x86_64 system by me.
Boot tested on an effect x86_64 system by customer.

Resolves BZ 264601.

Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Neil Horman <nhorman@redhat.com>
Acked-by: Jarod Wilson <jwilson@redhat.com>

diff --git a/arch/x86_64/kernel/pci-dma.c b/arch/x86_64/kernel/pci-dma.c
index dbe2b03..4f2915e 100644
--- a/arch/x86_64/kernel/pci-dma.c
+++ b/arch/x86_64/kernel/pci-dma.c
@@ -320,5 +320,10 @@ static int __init pci_iommu_init(void)
 	return 0;
 }
 
+void pci_iommu_shutdown(void)
+{
+	gart_iommu_shutdown();
+}
+
 /* Must execute after PCI subsystem */
 fs_initcall(pci_iommu_init);
diff --git a/arch/x86_64/kernel/pci-gart.c b/arch/x86_64/kernel/pci-gart.c
index aa986d5..565ee9b 100644
--- a/arch/x86_64/kernel/pci-gart.c
+++ b/arch/x86_64/kernel/pci-gart.c
@@ -574,6 +574,26 @@ static struct dma_mapping_ops gart_dma_ops = {
 	.unmap_sg = gart_unmap_sg,
 };
 
+void gart_iommu_shutdown(void)
+{
+	struct pci_dev *dev;
+	int i;
+
+	if (no_agp && (dma_ops != &gart_dma_ops))
+		return;
+
+        for (i = 0; i < num_k8_northbridges; i++) {
+                u32 ctl;
+
+                dev = k8_northbridges[i];
+                pci_read_config_dword(dev, 0x90, &ctl);
+
+                ctl &= ~1;
+
+                pci_write_config_dword(dev, 0x90, ctl);
+        }
+}
+
 void __init gart_iommu_init(void)
 { 
 	struct agp_kern_info info;
diff --git a/arch/x86_64/kernel/reboot.c b/arch/x86_64/kernel/reboot.c
index 2d67698..6f56f2f 100644
--- a/arch/x86_64/kernel/reboot.c
+++ b/arch/x86_64/kernel/reboot.c
@@ -15,6 +15,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/apic.h>
+#include <asm/proto.h>
 
 /*
  * Power off function, if any
@@ -80,6 +81,7 @@ static inline void kb_wait(void)
 void machine_shutdown(void)
 {
 	unsigned long flags;
+
 	/* Stop the cpus and apics */
 #ifdef CONFIG_SMP
 	int reboot_cpu_id;
@@ -110,6 +112,8 @@ void machine_shutdown(void)
 	disable_IO_APIC();
 
 	local_irq_restore(flags);
+
+	pci_iommu_shutdown();
 }
 
 void machine_emergency_restart(void)
diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index a10e5f1..4aa1c87 100644
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -111,11 +111,13 @@ extern int skip_ioapic_setup;
 extern int acpi_ht;
 extern int acpi_disabled;
 
+extern void pci_iommu_shutdown(void);
 extern void no_iommu_init(void);
 extern int force_iommu, no_iommu;
 extern int iommu_detected;
 #ifdef CONFIG_IOMMU
 extern void gart_iommu_init(void);
+extern void gart_iommu_shutdown(void);
 extern void gart_parse_options(char *);
 extern void iommu_hole_init(void);
 extern int fallback_aper_order;
@@ -127,6 +129,11 @@ extern int fix_aperture;
 #else
 #define iommu_aperture 0
 #define iommu_aperture_allowed 0
+
+static inline void gart_iommu_shutdown(void)
+{
+}
+
 #endif
 
 extern int reboot_force;