amd-iommu: disable IOMMU hardware on shutdown

When the IOMMU stays enabled the BIOS may not be able to finish the
machine shutdown properly. So disable the hardware on shutdown.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/include/asm/amd_iommu.h

@@ -29,9 +29,11 @@ extern void amd_iommu_detect(void);
 extern irqreturn_t amd_iommu_int_handler(int irq, void *data);
 extern void amd_iommu_flush_all_domains(void);
 extern void amd_iommu_flush_all_devices(void);
+extern void amd_iommu_shutdown(void);
 #else
 static inline int amd_iommu_init(void) { return -ENODEV; }
 static inline void amd_iommu_detect(void) { }
+static inline void amd_iommu_shutdown(void) { }
 #endif
 
 #endif /* _ASM_X86_AMD_IOMMU_H */

arch/x86/kernel/amd_iommu_init.c

@@ -1273,6 +1273,11 @@ int __init amd_iommu_init(void)
 	goto out;
 }
 
+void amd_iommu_shutdown(void)
+{
+	disable_iommus();
+}
+
 /****************************************************************************
  *
  * Early detect code. This code runs at IOMMU detection time in the DMA

arch/x86/kernel/pci-dma.c

@@ -290,6 +290,8 @@ static int __init pci_iommu_init(void)
 void pci_iommu_shutdown(void)
 {
 	gart_iommu_shutdown();
+
+	amd_iommu_shutdown();
 }
 /* Must execute after PCI subsystem */
 fs_initcall(pci_iommu_init);