arch/x86/kernel/pci-swiotlb.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/pci.h>
   4 #include <linux/cache.h>
   5 #include <linux/init.h>
   6 #include <linux/swiotlb.h>
   7 #include <linux/memblock.h>
   8 #include <linux/dma-direct.h>
   9 #include <linux/mem_encrypt.h>
  10
  11 #include <asm/iommu.h>
  12 #include <asm/swiotlb.h>
  13 #include <asm/dma.h>
  14 #include <asm/xen/swiotlb-xen.h>
  15 #include <asm/iommu_table.h>
  16
  17 int swiotlb __read_mostly;
  18
  19 /*
  20  * pci_swiotlb_detect_override - set swiotlb to 1 if necessary
  21  *
  22  * This returns non-zero if we are forced to use swiotlb (by the boot
  23  * option).
  24  */
  25 int __init pci_swiotlb_detect_override(void)
  26 {
  27         if (swiotlb_force == SWIOTLB_FORCE)
  28                 swiotlb = 1;
  29
  30         return swiotlb;
  31 }
  32 IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
  33                   pci_xen_swiotlb_detect,
  34                   pci_swiotlb_init,
  35                   pci_swiotlb_late_init);
  36
  37 /*
  38  * If 4GB or more detected (and iommu=off not set) or if SME is active
  39  * then set swiotlb to 1 and return 1.
  40  */
  41 int __init pci_swiotlb_detect_4gb(void)
  42 {
  43         /* don't initialize swiotlb if iommu=off (no_iommu=1) */
  44         if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
  45                 swiotlb = 1;
  46
  47         /*
  48          * If SME is active then swiotlb will be set to 1 so that bounce
  49          * buffers are allocated and used for devices that do not support
  50          * the addressing range required for the encryption mask.
  51          */
  52         if (sme_active())
  53                 swiotlb = 1;
  54
  55         return swiotlb;
  56 }
  57 IOMMU_INIT(pci_swiotlb_detect_4gb,
  58            pci_swiotlb_detect_override,
  59            pci_swiotlb_init,
  60            pci_swiotlb_late_init);
  61
  62 void __init pci_swiotlb_init(void)
  63 {
  64         if (swiotlb)
  65                 swiotlb_init(0);
  66 }
  67
  68 void __init pci_swiotlb_late_init(void)
  69 {
  70         /* An IOMMU turned us off. */
  71         if (!swiotlb)
  72                 swiotlb_exit();
  73         else {
  74                 printk(KERN_INFO "PCI-DMA: "
  75                        "Using software bounce buffering for IO (SWIOTLB)\n");
  76                 swiotlb_print_info();
  77         }
  78 }