1 /* 2 * Hard disk geometry utilities 3 * 4 * Copyright (C) 2012 Red Hat, Inc. 5 * 6 * This work is licensed under the terms of the GNU GPL, version 2 or later. 7 * See the COPYING file in the top-level directory. 8 * 9 * This file incorporates work covered by the following copyright and 10 * permission notice: 11 * 12 * Copyright (c) 2003 Fabrice Bellard 13 * 14 * Permission is hereby granted, free of charge, to any person obtaining a copy 15 * of this software and associated documentation files (the "Software"), to deal 16 * in the Software without restriction, including without limitation the rights 17 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 18 * copies of the Software, and to permit persons to whom the Software is 19 * furnished to do so, subject to the following conditions: 20 * 21 * The above copyright notice and this permission notice shall be included in 22 * all copies or substantial portions of the Software. 23 * 24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 27 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 29 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 30 * THE SOFTWARE. 31 */ 32 33 #include "sysemu/block-backend.h" 34 #include "hw/block/block.h" 35 #include "trace.h" 36 37 struct partition { 38 uint8_t boot_ind; /* 0x80 - active */ 39 uint8_t head; /* starting head */ 40 uint8_t sector; /* starting sector */ 41 uint8_t cyl; /* starting cylinder */ 42 uint8_t sys_ind; /* What partition type */ 43 uint8_t end_head; /* end head */ 44 uint8_t end_sector; /* end sector */ 45 uint8_t end_cyl; /* end cylinder */ 46 uint32_t start_sect; /* starting sector counting from 0 */ 47 uint32_t nr_sects; /* nr of sectors in partition */ 48 } QEMU_PACKED; 49 50 /* try to guess the disk logical geometry from the MSDOS partition table. 51 Return 0 if OK, -1 if could not guess */ 52 static int guess_disk_lchs(BlockBackend *blk, 53 int *pcylinders, int *pheads, int *psectors) 54 { 55 uint8_t buf[BDRV_SECTOR_SIZE]; 56 int i, heads, sectors, cylinders; 57 struct partition *p; 58 uint32_t nr_sects; 59 uint64_t nb_sectors; 60 61 blk_get_geometry(blk, &nb_sectors); 62 63 /** 64 * The function will be invoked during startup not only in sync I/O mode, 65 * but also in async I/O mode. So the I/O throttling function has to 66 * be disabled temporarily here, not permanently. 67 */ 68 if (blk_read_unthrottled(blk, 0, buf, 1) < 0) { 69 return -1; 70 } 71 /* test msdos magic */ 72 if (buf[510] != 0x55 || buf[511] != 0xaa) { 73 return -1; 74 } 75 for (i = 0; i < 4; i++) { 76 p = ((struct partition *)(buf + 0x1be)) + i; 77 nr_sects = le32_to_cpu(p->nr_sects); 78 if (nr_sects && p->end_head) { 79 /* We make the assumption that the partition terminates on 80 a cylinder boundary */ 81 heads = p->end_head + 1; 82 sectors = p->end_sector & 63; 83 if (sectors == 0) { 84 continue; 85 } 86 cylinders = nb_sectors / (heads * sectors); 87 if (cylinders < 1 || cylinders > 16383) { 88 continue; 89 } 90 *pheads = heads; 91 *psectors = sectors; 92 *pcylinders = cylinders; 93 trace_hd_geometry_lchs_guess(blk, cylinders, heads, sectors); 94 return 0; 95 } 96 } 97 return -1; 98 } 99 100 static void guess_chs_for_size(BlockBackend *blk, 101 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs) 102 { 103 uint64_t nb_sectors; 104 int cylinders; 105 106 blk_get_geometry(blk, &nb_sectors); 107 108 cylinders = nb_sectors / (16 * 63); 109 if (cylinders > 16383) { 110 cylinders = 16383; 111 } else if (cylinders < 2) { 112 cylinders = 2; 113 } 114 *pcyls = cylinders; 115 *pheads = 16; 116 *psecs = 63; 117 } 118 119 void hd_geometry_guess(BlockBackend *blk, 120 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs, 121 int *ptrans) 122 { 123 int cylinders, heads, secs, translation; 124 HDGeometry geo; 125 126 /* Try to probe the backing device geometry, otherwise fallback 127 to the old logic. (as of 12/2014 probing only succeeds on DASDs) */ 128 if (blk_probe_geometry(blk, &geo) == 0) { 129 *pcyls = geo.cylinders; 130 *psecs = geo.sectors; 131 *pheads = geo.heads; 132 translation = BIOS_ATA_TRANSLATION_NONE; 133 } else if (guess_disk_lchs(blk, &cylinders, &heads, &secs) < 0) { 134 /* no LCHS guess: use a standard physical disk geometry */ 135 guess_chs_for_size(blk, pcyls, pheads, psecs); 136 translation = hd_bios_chs_auto_trans(*pcyls, *pheads, *psecs); 137 } else if (heads > 16) { 138 /* LCHS guess with heads > 16 means that a BIOS LBA 139 translation was active, so a standard physical disk 140 geometry is OK */ 141 guess_chs_for_size(blk, pcyls, pheads, psecs); 142 translation = *pcyls * *pheads <= 131072 143 ? BIOS_ATA_TRANSLATION_LARGE 144 : BIOS_ATA_TRANSLATION_LBA; 145 } else { 146 /* LCHS guess with heads <= 16: use as physical geometry */ 147 *pcyls = cylinders; 148 *pheads = heads; 149 *psecs = secs; 150 /* disable any translation to be in sync with 151 the logical geometry */ 152 translation = BIOS_ATA_TRANSLATION_NONE; 153 } 154 if (ptrans) { 155 *ptrans = translation; 156 } 157 trace_hd_geometry_guess(blk, *pcyls, *pheads, *psecs, translation); 158 } 159 160 int hd_bios_chs_auto_trans(uint32_t cyls, uint32_t heads, uint32_t secs) 161 { 162 return cyls <= 1024 && heads <= 16 && secs <= 63 163 ? BIOS_ATA_TRANSLATION_NONE 164 : BIOS_ATA_TRANSLATION_LBA; 165 } 166