arch/x86/xen/mmu_hvm.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/types.h>
   3 #include <linux/crash_dump.h>
   4
   5 #include <xen/interface/xen.h>
   6 #include <xen/hvm.h>
   7
   8 #include "mmu.h"
   9
  10 #ifdef CONFIG_PROC_VMCORE
  11 /*
  12  * This function is used in two contexts:
  13  * - the kdump kernel has to check whether a pfn of the crashed kernel
  14  *   was a ballooned page. vmcore is using this function to decide
  15  *   whether to access a pfn of the crashed kernel.
  16  * - the kexec kernel has to check whether a pfn was ballooned by the
  17  *   previous kernel. If the pfn is ballooned, handle it properly.
  18  * Returns 0 if the pfn is not backed by a RAM page, the caller may
  19  * handle the pfn special in this case.
  20  */
  21 static int xen_oldmem_pfn_is_ram(unsigned long pfn)
  22 {
  23         struct xen_hvm_get_mem_type a = {
  24                 .domid = DOMID_SELF,
  25                 .pfn = pfn,
  26         };
  27         int ram;
  28
  29         if (HYPERVISOR_hvm_op(HVMOP_get_mem_type, &a))
  30                 return -ENXIO;
  31
  32         switch (a.mem_type) {
  33         case HVMMEM_mmio_dm:
  34                 ram = 0;
  35                 break;
  36         case HVMMEM_ram_rw:
  37         case HVMMEM_ram_ro:
  38         default:
  39                 ram = 1;
  40                 break;
  41         }
  42
  43         return ram;
  44 }
  45 #endif
  46
  47 static void xen_hvm_exit_mmap(struct mm_struct *mm)
  48 {
  49         struct xen_hvm_pagetable_dying a;
  50         int rc;
  51
  52         a.domid = DOMID_SELF;
  53         a.gpa = __pa(mm->pgd);
  54         rc = HYPERVISOR_hvm_op(HVMOP_pagetable_dying, &a);
  55         WARN_ON_ONCE(rc < 0);
  56 }
  57
  58 static int is_pagetable_dying_supported(void)
  59 {
  60         struct xen_hvm_pagetable_dying a;
  61         int rc = 0;
  62
  63         a.domid = DOMID_SELF;
  64         a.gpa = 0x00;
  65         rc = HYPERVISOR_hvm_op(HVMOP_pagetable_dying, &a);
  66         if (rc < 0) {
  67                 printk(KERN_DEBUG "HVMOP_pagetable_dying not supported\n");
  68                 return 0;
  69         }
  70         return 1;
  71 }
  72
  73 void __init xen_hvm_init_mmu_ops(void)
  74 {
  75         if (is_pagetable_dying_supported())
  76                 pv_mmu_ops.exit_mmap = xen_hvm_exit_mmap;
  77 #ifdef CONFIG_PROC_VMCORE
  78         register_oldmem_pfn_is_ram(&xen_oldmem_pfn_is_ram);
  79 #endif
  80 }