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 // SPDX-License-Identifier: GPL-2.0
 /*
  * Machine specific setup for xen
  *
  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
  */
 
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/pm.h>
 #include <linux/memblock.h>
 #include <linux/cpuidle.h>
 #include <linux/cpufreq.h>
 #include <linux/memory_hotplug.h>
 
 #include <asm/elf.h>
 #include <asm/vdso.h>
 #include <asm/e820/api.h>
 #include <asm/setup.h>
 #include <asm/acpi.h>
 #include <asm/numa.h>
 #include <asm/idtentry.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 
 #include <xen/xen.h>
 #include <xen/page.h>
 #include <xen/interface/callback.h>
 #include <xen/interface/memory.h>
 #include <xen/interface/physdev.h>
 #include <xen/features.h>
 #include <xen/hvc-console.h>
 #include "xen-ops.h"
 #include "mmu.h"
 
 #define GB(x) ((uint64_t)(x) * 1024 * 1024 * 1024)
 
 /* Amount of extra memory space we add to the e820 ranges */
 struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
 
 /* Number of pages released from the initial allocation. */
 unsigned long xen_released_pages;
 
 /* E820 map used during setting up memory. */
 static struct e820_table xen_e820_table __initdata;
 
 /*
  * Buffer used to remap identity mapped pages. We only need the virtual space.
  * The physical page behind this address is remapped as needed to different
  * buffer pages.
  */
 #define REMAP_SIZE  (P2M_PER_PAGE - 3)
 static struct {
     unsigned long   next_area_mfn;
     unsigned long   target_pfn;
     unsigned long   size;
     unsigned long   mfns[REMAP_SIZE];
 } xen_remap_buf __initdata __aligned(PAGE_SIZE);
 static unsigned long xen_remap_mfn __initdata = INVALID_P2M_ENTRY;
 
 /*
  * The maximum amount of extra memory compared to the base size.  The
  * main scaling factor is the size of struct page.  At extreme ratios
  * of base:extra, all the base memory can be filled with page
  * structures for the extra memory, leaving no space for anything
  * else.
  *
  * 10x seems like a reasonable balance between scaling flexibility and
  * leaving a practically usable system.
  */
 #define EXTRA_MEM_RATIO     (10)
 
 static bool xen_512gb_limit __initdata = IS_ENABLED(CONFIG_XEN_512GB);
 
 static void __init xen_parse_512gb(void)
 {
     bool val = false;
     char *arg;
 
     arg = strstr(xen_start_info->cmd_line, "xen_512gb_limit");
     if (!arg)
         return;
 
     arg = strstr(xen_start_info->cmd_line, "xen_512gb_limit=");
     if (!arg)
         val = true;
     else if (strtobool(arg + strlen("xen_512gb_limit="), &val))
         return;
 
     xen_512gb_limit = val;
 }
 
 static void __init xen_add_extra_mem(unsigned long start_pfn,
                      unsigned long n_pfns)
 {
     int i;
 
     /*
      * No need to check for zero size, should happen rarely and will only
      * write a new entry regarded to be unused due to zero size.
      */
     for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
         /* Add new region. */
         if (xen_extra_mem[i].n_pfns == 0) {
             xen_extra_mem[i].start_pfn = start_pfn;
             xen_extra_mem[i].n_pfns = n_pfns;
             break;
         }
         /* Append to existing region. */
         if (xen_extra_mem[i].start_pfn + xen_extra_mem[i].n_pfns ==
             start_pfn) {
             xen_extra_mem[i].n_pfns += n_pfns;
             break;
         }
     }
     if (i == XEN_EXTRA_MEM_MAX_REGIONS)
         printk(KERN_WARNING "Warning: not enough extra memory regions\n");
 
     memblock_reserve(PFN_PHYS(start_pfn), PFN_PHYS(n_pfns));
 }
 
 static void __init xen_del_extra_mem(unsigned long start_pfn,
                      unsigned long n_pfns)
 {
     int i;
     unsigned long start_r, size_r;
 
     for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
         start_r = xen_extra_mem[i].start_pfn;
         size_r = xen_extra_mem[i].n_pfns;
 
         /* Start of region. */
         if (start_r == start_pfn) {
             BUG_ON(n_pfns > size_r);
             xen_extra_mem[i].start_pfn += n_pfns;
             xen_extra_mem[i].n_pfns -= n_pfns;
             break;
         }
         /* End of region. */
         if (start_r + size_r == start_pfn + n_pfns) {
             BUG_ON(n_pfns > size_r);
             xen_extra_mem[i].n_pfns -= n_pfns;
             break;
         }
         /* Mid of region. */
         if (start_pfn > start_r && start_pfn < start_r + size_r) {
             BUG_ON(start_pfn + n_pfns > start_r + size_r);
             xen_extra_mem[i].n_pfns = start_pfn - start_r;
             /* Calling memblock_reserve() again is okay. */
             xen_add_extra_mem(start_pfn + n_pfns, start_r + size_r -
                       (start_pfn + n_pfns));
             break;
         }
     }
     memblock_phys_free(PFN_PHYS(start_pfn), PFN_PHYS(n_pfns));
 }
 
 /*
  * Called during boot before the p2m list can take entries beyond the
  * hypervisor supplied p2m list. Entries in extra mem are to be regarded as
  * invalid.
  */
 unsigned long __ref xen_chk_extra_mem(unsigned long pfn)
 {
     int i;
 
     for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
         if (pfn >= xen_extra_mem[i].start_pfn &&
             pfn < xen_extra_mem[i].start_pfn + xen_extra_mem[i].n_pfns)
             return INVALID_P2M_ENTRY;
     }
 
     return IDENTITY_FRAME(pfn);
 }
 
 /*
  * Mark all pfns of extra mem as invalid in p2m list.
  */
 void __init xen_inv_extra_mem(void)
 {
     unsigned long pfn, pfn_s, pfn_e;
     int i;
 
     for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
         if (!xen_extra_mem[i].n_pfns)
             continue;
         pfn_s = xen_extra_mem[i].start_pfn;
         pfn_e = pfn_s + xen_extra_mem[i].n_pfns;
         for (pfn = pfn_s; pfn < pfn_e; pfn++)
             set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
     }
 }
 
 /*
  * Finds the next RAM pfn available in the E820 map after min_pfn.
  * This function updates min_pfn with the pfn found and returns
  * the size of that range or zero if not found.
  */
 static unsigned long __init xen_find_pfn_range(unsigned long *min_pfn)
 {
     const struct e820_entry *entry = xen_e820_table.entries;
     unsigned int i;
     unsigned long done = 0;
 
     for (i = 0; i < xen_e820_table.nr_entries; i++, entry++) {
         unsigned long s_pfn;
         unsigned long e_pfn;
 
         if (entry->type != E820_TYPE_RAM)
             continue;
 
         e_pfn = PFN_DOWN(entry->addr + entry->size);
 
         /* We only care about E820 after this */
         if (e_pfn <= *min_pfn)
             continue;
 
         s_pfn = PFN_UP(entry->addr);
 
         /* If min_pfn falls within the E820 entry, we want to start
          * at the min_pfn PFN.
          */
         if (s_pfn <= *min_pfn) {
             done = e_pfn - *min_pfn;
         } else {
             done = e_pfn - s_pfn;
             *min_pfn = s_pfn;
         }
         break;
     }
 
     return done;
 }
 
 static int __init xen_free_mfn(unsigned long mfn)
 {
     struct xen_memory_reservation reservation = {
         .address_bits = 0,
         .extent_order = 0,
         .domid        = DOMID_SELF
     };
 
     set_xen_guest_handle(reservation.extent_start, &mfn);
     reservation.nr_extents = 1;
 
     return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 }
 
 /*
  * This releases a chunk of memory and then does the identity map. It's used
  * as a fallback if the remapping fails.
  */
 static void __init xen_set_identity_and_release_chunk(unsigned long start_pfn,
             unsigned long end_pfn, unsigned long nr_pages)
 {
     unsigned long pfn, end;
     int ret;
 
     WARN_ON(start_pfn > end_pfn);
 
     /* Release pages first. */
     end = min(end_pfn, nr_pages);
     for (pfn = start_pfn; pfn < end; pfn++) {
         unsigned long mfn = pfn_to_mfn(pfn);
 
         /* Make sure pfn exists to start with */
         if (mfn == INVALID_P2M_ENTRY || mfn_to_pfn(mfn) != pfn)
             continue;
 
         ret = xen_free_mfn(mfn);
         WARN(ret != 1, "Failed to release pfn %lx err=%d\n", pfn, ret);
 
         if (ret == 1) {
             xen_released_pages++;
             if (!__set_phys_to_machine(pfn, INVALID_P2M_ENTRY))
                 break;
         } else
             break;
     }
 
     set_phys_range_identity(start_pfn, end_pfn);
 }
 
 /*
  * Helper function to update the p2m and m2p tables and kernel mapping.
  */
 static void __init xen_update_mem_tables(unsigned long pfn, unsigned long mfn)
 {
     struct mmu_update update = {
         .ptr = ((uint64_t)mfn << PAGE_SHIFT) | MMU_MACHPHYS_UPDATE,
         .val = pfn
     };
 
     /* Update p2m */
     if (!set_phys_to_machine(pfn, mfn)) {
         WARN(1, "Failed to set p2m mapping for pfn=%ld mfn=%ld\n",
              pfn, mfn);
         BUG();
     }
 
     /* Update m2p */
     if (HYPERVISOR_mmu_update(&update, 1, NULL, DOMID_SELF) < 0) {
         WARN(1, "Failed to set m2p mapping for mfn=%ld pfn=%ld\n",
              mfn, pfn);
         BUG();
     }
 
     if (HYPERVISOR_update_va_mapping((unsigned long)__va(pfn << PAGE_SHIFT),
                      mfn_pte(mfn, PAGE_KERNEL), 0)) {
         WARN(1, "Failed to update kernel mapping for mfn=%ld pfn=%ld\n",
               mfn, pfn);
         BUG();
     }
 }
 
 /*
  * This function updates the p2m and m2p tables with an identity map from
  * start_pfn to start_pfn+size and prepares remapping the underlying RAM of the
  * original allocation at remap_pfn. The information needed for remapping is
  * saved in the memory itself to avoid the need for allocating buffers. The
  * complete remap information is contained in a list of MFNs each containing
  * up to REMAP_SIZE MFNs and the start target PFN for doing the remap.
  * This enables us to preserve the original mfn sequence while doing the
  * remapping at a time when the memory management is capable of allocating
  * virtual and physical memory in arbitrary amounts, see 'xen_remap_memory' and
  * its callers.
  */
 static void __init xen_do_set_identity_and_remap_chunk(
         unsigned long start_pfn, unsigned long size, unsigned long remap_pfn)
 {
     unsigned long buf = (unsigned long)&xen_remap_buf;
     unsigned long mfn_save, mfn;
     unsigned long ident_pfn_iter, remap_pfn_iter;
     unsigned long ident_end_pfn = start_pfn + size;
     unsigned long left = size;
     unsigned int i, chunk;
 
     WARN_ON(size == 0);
 
     mfn_save = virt_to_mfn(buf);
 
     for (ident_pfn_iter = start_pfn, remap_pfn_iter = remap_pfn;
          ident_pfn_iter < ident_end_pfn;
          ident_pfn_iter += REMAP_SIZE, remap_pfn_iter += REMAP_SIZE) {
         chunk = (left < REMAP_SIZE) ? left : REMAP_SIZE;
 
         /* Map first pfn to xen_remap_buf */
         mfn = pfn_to_mfn(ident_pfn_iter);
         set_pte_mfn(buf, mfn, PAGE_KERNEL);
 
         /* Save mapping information in page */
         xen_remap_buf.next_area_mfn = xen_remap_mfn;
         xen_remap_buf.target_pfn = remap_pfn_iter;
         xen_remap_buf.size = chunk;
         for (i = 0; i < chunk; i++)
             xen_remap_buf.mfns[i] = pfn_to_mfn(ident_pfn_iter + i);
 
         /* Put remap buf into list. */
         xen_remap_mfn = mfn;
 
         /* Set identity map */
         set_phys_range_identity(ident_pfn_iter, ident_pfn_iter + chunk);
 
         left -= chunk;
     }
 
     /* Restore old xen_remap_buf mapping */
     set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
 }
 
 /*
  * This function takes a contiguous pfn range that needs to be identity mapped
  * and:
  *
  *  1) Finds a new range of pfns to use to remap based on E820 and remap_pfn.
  *  2) Calls the do_ function to actually do the mapping/remapping work.
  *
  * The goal is to not allocate additional memory but to remap the existing
  * pages. In the case of an error the underlying memory is simply released back
  * to Xen and not remapped.
  */
 static unsigned long __init xen_set_identity_and_remap_chunk(
     unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
     unsigned long remap_pfn)
 {
     unsigned long pfn;
     unsigned long i = 0;
     unsigned long n = end_pfn - start_pfn;
 
     if (remap_pfn == 0)
         remap_pfn = nr_pages;
 
     while (i < n) {
         unsigned long cur_pfn = start_pfn + i;
         unsigned long left = n - i;
         unsigned long size = left;
         unsigned long remap_range_size;
 
         /* Do not remap pages beyond the current allocation */
         if (cur_pfn >= nr_pages) {
             /* Identity map remaining pages */
             set_phys_range_identity(cur_pfn, cur_pfn + size);
             break;
         }
         if (cur_pfn + size > nr_pages)
             size = nr_pages - cur_pfn;
 
         remap_range_size = xen_find_pfn_range(&remap_pfn);
         if (!remap_range_size) {
             pr_warn("Unable to find available pfn range, not remapping identity pages\n");
             xen_set_identity_and_release_chunk(cur_pfn,
                         cur_pfn + left, nr_pages);
             break;
         }
         /* Adjust size to fit in current e820 RAM region */
         if (size > remap_range_size)
             size = remap_range_size;
 
         xen_do_set_identity_and_remap_chunk(cur_pfn, size, remap_pfn);
 
         /* Update variables to reflect new mappings. */
         i += size;
         remap_pfn += size;
     }
 
     /*
      * If the PFNs are currently mapped, their VA mappings need to be
      * zapped.
      */
     for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++)
         (void)HYPERVISOR_update_va_mapping(
             (unsigned long)__va(pfn << PAGE_SHIFT),
             native_make_pte(0), 0);
 
     return remap_pfn;
 }
 
 static unsigned long __init xen_count_remap_pages(
     unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
     unsigned long remap_pages)
 {
     if (start_pfn >= nr_pages)
         return remap_pages;
 
     return remap_pages + min(end_pfn, nr_pages) - start_pfn;
 }
 
 static unsigned long __init xen_foreach_remap_area(unsigned long nr_pages,
     unsigned long (*func)(unsigned long start_pfn, unsigned long end_pfn,
                   unsigned long nr_pages, unsigned long last_val))
 {
     phys_addr_t start = 0;
     unsigned long ret_val = 0;
     const struct e820_entry *entry = xen_e820_table.entries;
     int i;
 
     /*
      * Combine non-RAM regions and gaps until a RAM region (or the
      * end of the map) is reached, then call the provided function
      * to perform its duty on the non-RAM region.
      *
      * The combined non-RAM regions are rounded to a whole number
      * of pages so any partial pages are accessible via the 1:1
      * mapping.  This is needed for some BIOSes that put (for
      * example) the DMI tables in a reserved region that begins on
      * a non-page boundary.
      */
     for (i = 0; i < xen_e820_table.nr_entries; i++, entry++) {
         phys_addr_t end = entry->addr + entry->size;
         if (entry->type == E820_TYPE_RAM || i == xen_e820_table.nr_entries - 1) {
             unsigned long start_pfn = PFN_DOWN(start);
             unsigned long end_pfn = PFN_UP(end);
 
             if (entry->type == E820_TYPE_RAM)
                 end_pfn = PFN_UP(entry->addr);
 
             if (start_pfn < end_pfn)
                 ret_val = func(start_pfn, end_pfn, nr_pages,
                            ret_val);
             start = end;
         }
     }
 
     return ret_val;
 }
 
 /*
  * Remap the memory prepared in xen_do_set_identity_and_remap_chunk().
  * The remap information (which mfn remap to which pfn) is contained in the
  * to be remapped memory itself in a linked list anchored at xen_remap_mfn.
  * This scheme allows to remap the different chunks in arbitrary order while
  * the resulting mapping will be independent from the order.
  */
 void __init xen_remap_memory(void)
 {
     unsigned long buf = (unsigned long)&xen_remap_buf;
     unsigned long mfn_save, pfn;
     unsigned long remapped = 0;
     unsigned int i;
     unsigned long pfn_s = ~0UL;
     unsigned long len = 0;
 
     mfn_save = virt_to_mfn(buf);
 
     while (xen_remap_mfn != INVALID_P2M_ENTRY) {
         /* Map the remap information */
         set_pte_mfn(buf, xen_remap_mfn, PAGE_KERNEL);
 
         BUG_ON(xen_remap_mfn != xen_remap_buf.mfns[0]);
 
         pfn = xen_remap_buf.target_pfn;
         for (i = 0; i < xen_remap_buf.size; i++) {
             xen_update_mem_tables(pfn, xen_remap_buf.mfns[i]);
             remapped++;
             pfn++;
         }
         if (pfn_s == ~0UL || pfn == pfn_s) {
             pfn_s = xen_remap_buf.target_pfn;
             len += xen_remap_buf.size;
         } else if (pfn_s + len == xen_remap_buf.target_pfn) {
             len += xen_remap_buf.size;
         } else {
             xen_del_extra_mem(pfn_s, len);
             pfn_s = xen_remap_buf.target_pfn;
             len = xen_remap_buf.size;
         }
         xen_remap_mfn = xen_remap_buf.next_area_mfn;
     }
 
     if (pfn_s != ~0UL && len)
         xen_del_extra_mem(pfn_s, len);
 
     set_pte_mfn(buf, mfn_save, PAGE_KERNEL);
 
     pr_info("Remapped %ld page(s)\n", remapped);
 }
 
 static unsigned long __init xen_get_pages_limit(void)
 {
     unsigned long limit;
 
     limit = MAXMEM / PAGE_SIZE;
     if (!xen_initial_domain() && xen_512gb_limit)
         limit = GB(512) / PAGE_SIZE;
 
     return limit;
 }
 
 static unsigned long __init xen_get_max_pages(void)
 {
     unsigned long max_pages, limit;
     domid_t domid = DOMID_SELF;
     long ret;
 
     limit = xen_get_pages_limit();
     max_pages = limit;
 
     /*
      * For the initial domain we use the maximum reservation as
      * the maximum page.
      *
      * For guest domains the current maximum reservation reflects
      * the current maximum rather than the static maximum. In this
      * case the e820 map provided to us will cover the static
      * maximum region.
      */
     if (xen_initial_domain()) {
         ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid);
         if (ret > 0)
             max_pages = ret;
     }
 
     return min(max_pages, limit);
 }
 
 static void __init xen_align_and_add_e820_region(phys_addr_t start,
                          phys_addr_t size, int type)
 {
     phys_addr_t end = start + size;
 
     /* Align RAM regions to page boundaries. */
     if (type == E820_TYPE_RAM) {
         start = PAGE_ALIGN(start);
         end &= ~((phys_addr_t)PAGE_SIZE - 1);
 #ifdef CONFIG_MEMORY_HOTPLUG
         /*
          * Don't allow adding memory not in E820 map while booting the
          * system. Once the balloon driver is up it will remove that
          * restriction again.
          */
         max_mem_size = end;
 #endif
     }
 
     e820__range_add(start, end - start, type);
 }
 
 static void __init xen_ignore_unusable(void)
 {
     struct e820_entry *entry = xen_e820_table.entries;
     unsigned int i;
 
     for (i = 0; i < xen_e820_table.nr_entries; i++, entry++) {
         if (entry->type == E820_TYPE_UNUSABLE)
             entry->type = E820_TYPE_RAM;
     }
 }
 
 bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size)
 {
     struct e820_entry *entry;
     unsigned mapcnt;
     phys_addr_t end;
 
     if (!size)
         return false;
 
     end = start + size;
     entry = xen_e820_table.entries;
 
     for (mapcnt = 0; mapcnt < xen_e820_table.nr_entries; mapcnt++) {
         if (entry->type == E820_TYPE_RAM && entry->addr <= start &&
             (entry->addr + entry->size) >= end)
             return false;
 
         entry++;
     }
 
     return true;
 }
 
 /*
  * Find a free area in physical memory not yet reserved and compliant with
  * E820 map.
  * Used to relocate pre-allocated areas like initrd or p2m list which are in
  * conflict with the to be used E820 map.
  * In case no area is found, return 0. Otherwise return the physical address
  * of the area which is already reserved for convenience.
  */
 phys_addr_t __init xen_find_free_area(phys_addr_t size)
 {
     unsigned mapcnt;
     phys_addr_t addr, start;
     struct e820_entry *entry = xen_e820_table.entries;
 
     for (mapcnt = 0; mapcnt < xen_e820_table.nr_entries; mapcnt++, entry++) {
         if (entry->type != E820_TYPE_RAM || entry->size < size)
             continue;
         start = entry->addr;
         for (addr = start; addr < start + size; addr += PAGE_SIZE) {
             if (!memblock_is_reserved(addr))
                 continue;
             start = addr + PAGE_SIZE;
             if (start + size > entry->addr + entry->size)
                 break;
         }
         if (addr >= start + size) {
             memblock_reserve(start, size);
             return start;
         }
     }
 
     return 0;
 }
 
 /*
  * Like memcpy, but with physical addresses for dest and src.
  */
 static void __init xen_phys_memcpy(phys_addr_t dest, phys_addr_t src,
                    phys_addr_t n)
 {
     phys_addr_t dest_off, src_off, dest_len, src_len, len;
     void *from, *to;
 
     while (n) {
         dest_off = dest & ~PAGE_MASK;
         src_off = src & ~PAGE_MASK;
         dest_len = n;
         if (dest_len > (NR_FIX_BTMAPS << PAGE_SHIFT) - dest_off)
             dest_len = (NR_FIX_BTMAPS << PAGE_SHIFT) - dest_off;
         src_len = n;
         if (src_len > (NR_FIX_BTMAPS << PAGE_SHIFT) - src_off)
             src_len = (NR_FIX_BTMAPS << PAGE_SHIFT) - src_off;
         len = min(dest_len, src_len);
         to = early_memremap(dest - dest_off, dest_len + dest_off);
         from = early_memremap(src - src_off, src_len + src_off);
         memcpy(to, from, len);
         early_memunmap(to, dest_len + dest_off);
         early_memunmap(from, src_len + src_off);
         n -= len;
         dest += len;
         src += len;
     }
 }
 
 /*
  * Reserve Xen mfn_list.
  */
 static void __init xen_reserve_xen_mfnlist(void)
 {
     phys_addr_t start, size;
 
     if (xen_start_info->mfn_list >= __START_KERNEL_map) {
         start = __pa(xen_start_info->mfn_list);
         size = PFN_ALIGN(xen_start_info->nr_pages *
                  sizeof(unsigned long));
     } else {
         start = PFN_PHYS(xen_start_info->first_p2m_pfn);
         size = PFN_PHYS(xen_start_info->nr_p2m_frames);
     }
 
     memblock_reserve(start, size);
     if (!xen_is_e820_reserved(start, size))
         return;
 
     xen_relocate_p2m();
     memblock_phys_free(start, size);
 }
 
 /**
  * xen_memory_setup - Hook for machine specific memory setup.
  **/
 char * __init xen_memory_setup(void)
 {
     unsigned long max_pfn, pfn_s, n_pfns;
     phys_addr_t mem_end, addr, size, chunk_size;
     u32 type;
     int rc;
     struct xen_memory_map memmap;
     unsigned long max_pages;
     unsigned long extra_pages = 0;
     int i;
     int op;
 
     xen_parse_512gb();
     max_pfn = xen_get_pages_limit();
     max_pfn = min(max_pfn, xen_start_info->nr_pages);
     mem_end = PFN_PHYS(max_pfn);
 
     memmap.nr_entries = ARRAY_SIZE(xen_e820_table.entries);
     set_xen_guest_handle(memmap.buffer, xen_e820_table.entries);
 
 #if defined(CONFIG_MEMORY_HOTPLUG) && defined(CONFIG_XEN_BALLOON)
     xen_saved_max_mem_size = max_mem_size;
 #endif
 
     op = xen_initial_domain() ?
         XENMEM_machine_memory_map :
         XENMEM_memory_map;
     rc = HYPERVISOR_memory_op(op, &memmap);
     if (rc == -ENOSYS) {
         BUG_ON(xen_initial_domain());
         memmap.nr_entries = 1;
         xen_e820_table.entries[0].addr = 0ULL;
         xen_e820_table.entries[0].size = mem_end;
         /* 8MB slack (to balance backend allocations). */
         xen_e820_table.entries[0].size += 8ULL << 20;
         xen_e820_table.entries[0].type = E820_TYPE_RAM;
         rc = 0;
     }
     BUG_ON(rc);
     BUG_ON(memmap.nr_entries == 0);
     xen_e820_table.nr_entries = memmap.nr_entries;
 
     /*
      * Xen won't allow a 1:1 mapping to be created to UNUSABLE
      * regions, so if we're using the machine memory map leave the
      * region as RAM as it is in the pseudo-physical map.
      *
      * UNUSABLE regions in domUs are not handled and will need
      * a patch in the future.
      */
     if (xen_initial_domain())
         xen_ignore_unusable();
 
     /* Make sure the Xen-supplied memory map is well-ordered. */
     e820__update_table(&xen_e820_table);
 
     max_pages = xen_get_max_pages();
 
     /* How many extra pages do we need due to remapping? */
     max_pages += xen_foreach_remap_area(max_pfn, xen_count_remap_pages);
 
     if (max_pages > max_pfn)
         extra_pages += max_pages - max_pfn;
 
     /*
      * Clamp the amount of extra memory to a EXTRA_MEM_RATIO
      * factor the base size.
      *
      * Make sure we have no memory above max_pages, as this area
      * isn't handled by the p2m management.
      */
     extra_pages = min3(EXTRA_MEM_RATIO * min(max_pfn, PFN_DOWN(MAXMEM)),
                extra_pages, max_pages - max_pfn);
     i = 0;
     addr = xen_e820_table.entries[0].addr;
     size = xen_e820_table.entries[0].size;
     while (i < xen_e820_table.nr_entries) {
         bool discard = false;
 
         chunk_size = size;
         type = xen_e820_table.entries[i].type;
 
         if (type == E820_TYPE_RAM) {
             if (addr < mem_end) {
                 chunk_size = min(size, mem_end - addr);
             } else if (extra_pages) {
                 chunk_size = min(size, PFN_PHYS(extra_pages));
                 pfn_s = PFN_UP(addr);
                 n_pfns = PFN_DOWN(addr + chunk_size) - pfn_s;
                 extra_pages -= n_pfns;
                 xen_add_extra_mem(pfn_s, n_pfns);
                 xen_max_p2m_pfn = pfn_s + n_pfns;
             } else
                 discard = true;
         }
 
         if (!discard)
             xen_align_and_add_e820_region(addr, chunk_size, type);
 
         addr += chunk_size;
         size -= chunk_size;
         if (size == 0) {
             i++;
             if (i < xen_e820_table.nr_entries) {
                 addr = xen_e820_table.entries[i].addr;
                 size = xen_e820_table.entries[i].size;
             }
         }
     }
 
     /*
      * Set the rest as identity mapped, in case PCI BARs are
      * located here.
      */
     set_phys_range_identity(addr / PAGE_SIZE, ~0ul);
 
     /*
      * In domU, the ISA region is normal, usable memory, but we
      * reserve ISA memory anyway because too many things poke
      * about in there.
      */
     e820__range_add(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS, E820_TYPE_RESERVED);
 
     e820__update_table(e820_table);
 
     /*
      * Check whether the kernel itself conflicts with the target E820 map.
      * Failing now is better than running into weird problems later due
      * to relocating (and even reusing) pages with kernel text or data.
      */
     if (xen_is_e820_reserved(__pa_symbol(_text),
             __pa_symbol(__bss_stop) - __pa_symbol(_text))) {
         xen_raw_console_write("Xen hypervisor allocated kernel memory conflicts with E820 map\n");
         BUG();
     }
 
     /*
      * Check for a conflict of the hypervisor supplied page tables with
      * the target E820 map.
      */
     xen_pt_check_e820();
 
     xen_reserve_xen_mfnlist();
 
     /* Check for a conflict of the initrd with the target E820 map. */
     if (xen_is_e820_reserved(boot_params.hdr.ramdisk_image,
                  boot_params.hdr.ramdisk_size)) {
         phys_addr_t new_area, start, size;
 
         new_area = xen_find_free_area(boot_params.hdr.ramdisk_size);
         if (!new_area) {
             xen_raw_console_write("Can't find new memory area for initrd needed due to E820 map conflict\n");
             BUG();
         }
 
         start = boot_params.hdr.ramdisk_image;
         size = boot_params.hdr.ramdisk_size;
         xen_phys_memcpy(new_area, start, size);
         pr_info("initrd moved from [mem %#010llx-%#010llx] to [mem %#010llx-%#010llx]\n",
             start, start + size, new_area, new_area + size);
         memblock_phys_free(start, size);
         boot_params.hdr.ramdisk_image = new_area;
         boot_params.ext_ramdisk_image = new_area >> 32;
     }
 
     /*
      * Set identity map on non-RAM pages and prepare remapping the
      * underlying RAM.
      */
     xen_foreach_remap_area(max_pfn, xen_set_identity_and_remap_chunk);
 
     pr_info("Released %ld page(s)\n", xen_released_pages);
 
     return "Xen";
 }
 
 static int register_callback(unsigned type, const void *func)
 {
     struct callback_register callback = {
         .type = type,
         .address = XEN_CALLBACK(__KERNEL_CS, func),
         .flags = CALLBACKF_mask_events,
     };
 
     return HYPERVISOR_callback_op(CALLBACKOP_register, &callback);
 }
 
 void xen_enable_sysenter(void)
 {
     int ret;
     unsigned sysenter_feature;
 
     sysenter_feature = X86_FEATURE_SYSENTER32;
 
     if (!boot_cpu_has(sysenter_feature))
         return;
 
     ret = register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat);
     if(ret != 0)
         setup_clear_cpu_cap(sysenter_feature);
 }
 
 void xen_enable_syscall(void)
 {
     int ret;
 
     ret = register_callback(CALLBACKTYPE_syscall, xen_entry_SYSCALL_64);
     if (ret != 0) {
         printk(KERN_ERR "Failed to set syscall callback: %d\n", ret);
         /* Pretty fatal; 64-bit userspace has no other
            mechanism for syscalls. */
     }
 
     if (boot_cpu_has(X86_FEATURE_SYSCALL32)) {
         ret = register_callback(CALLBACKTYPE_syscall32,
                     xen_entry_SYSCALL_compat);
         if (ret != 0)
             setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
     }
 }
 
 static void __init xen_pvmmu_arch_setup(void)
 {
     HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_4gb_segments);
     HYPERVISOR_vm_assist(VMASST_CMD_enable, VMASST_TYPE_writable_pagetables);
 
     HYPERVISOR_vm_assist(VMASST_CMD_enable,
                  VMASST_TYPE_pae_extended_cr3);
 
     if (register_callback(CALLBACKTYPE_event,
                   xen_asm_exc_xen_hypervisor_callback) ||
         register_callback(CALLBACKTYPE_failsafe, xen_failsafe_callback))
         BUG();
 
     xen_enable_sysenter();
     xen_enable_syscall();
 }
 
 /* This function is not called for HVM domains */
 void __init xen_arch_setup(void)
 {
     xen_panic_handler_init();
     xen_pvmmu_arch_setup();
 
 #ifdef CONFIG_ACPI
     if (!(xen_start_info->flags & SIF_INITDOMAIN)) {
         printk(KERN_INFO "ACPI in unprivileged domain disabled\n");
         disable_acpi();
     }
 #endif
 
     memcpy(boot_command_line, xen_start_info->cmd_line,
            MAX_GUEST_CMDLINE > COMMAND_LINE_SIZE ?
            COMMAND_LINE_SIZE : MAX_GUEST_CMDLINE);
 
     /* Set up idle, making sure it calls safe_halt() pvop */
     disable_cpuidle();
     disable_cpufreq();
     WARN_ON(xen_set_default_idle());
 #ifdef CONFIG_NUMA
     numa_off = 1;
 #endif
 }

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