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 "qemu/osdep.h" 34 #include "sysemu/block-backend.h" 35 #include "qapi/qapi-types-block.h" 36 #include "qemu/bswap.h" 37 #include "hw/block/block.h" 38 #include "trace.h" 39 40 struct partition { 41 uint8_t boot_ind; /* 0x80 - active */ 42 uint8_t head; /* starting head */ 43 uint8_t sector; /* starting sector */ 44 uint8_t cyl; /* starting cylinder */ 45 uint8_t sys_ind; /* What partition type */ 46 uint8_t end_head; /* end head */ 47 uint8_t end_sector; /* end sector */ 48 uint8_t end_cyl; /* end cylinder */ 49 uint32_t start_sect; /* starting sector counting from 0 */ 50 uint32_t nr_sects; /* nr of sectors in partition */ 51 } QEMU_PACKED; 52 53 /* try to guess the disk logical geometry from the MSDOS partition table. 54 Return 0 if OK, -1 if could not guess */ 55 static int guess_disk_lchs(BlockBackend *blk, 56 int *pcylinders, int *pheads, int *psectors) 57 { 58 uint8_t buf[BDRV_SECTOR_SIZE]; 59 int i, heads, sectors, cylinders; 60 struct partition *p; 61 uint32_t nr_sects; 62 uint64_t nb_sectors; 63 64 blk_get_geometry(blk, &nb_sectors); 65 66 /** 67 * The function will be invoked during startup not only in sync I/O mode, 68 * but also in async I/O mode. So the I/O throttling function has to 69 * be disabled temporarily here, not permanently. 70 */ 71 if (blk_pread_unthrottled(blk, 0, buf, BDRV_SECTOR_SIZE) < 0) { 72 return -1; 73 } 74 /* test msdos magic */ 75 if (buf[510] != 0x55 || buf[511] != 0xaa) { 76 return -1; 77 } 78 for (i = 0; i < 4; i++) { 79 p = ((struct partition *)(buf + 0x1be)) + i; 80 nr_sects = le32_to_cpu(p->nr_sects); 81 if (nr_sects && p->end_head) { 82 /* We make the assumption that the partition terminates on 83 a cylinder boundary */ 84 heads = p->end_head + 1; 85 sectors = p->end_sector & 63; 86 if (sectors == 0) { 87 continue; 88 } 89 cylinders = nb_sectors / (heads * sectors); 90 if (cylinders < 1 || cylinders > 16383) { 91 continue; 92 } 93 *pheads = heads; 94 *psectors = sectors; 95 *pcylinders = cylinders; 96 trace_hd_geometry_lchs_guess(blk, cylinders, heads, sectors); 97 return 0; 98 } 99 } 100 return -1; 101 } 102 103 static void guess_chs_for_size(BlockBackend *blk, 104 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs) 105 { 106 uint64_t nb_sectors; 107 int cylinders; 108 109 blk_get_geometry(blk, &nb_sectors); 110 111 cylinders = nb_sectors / (16 * 63); 112 if (cylinders > 16383) { 113 cylinders = 16383; 114 } else if (cylinders < 2) { 115 cylinders = 2; 116 } 117 *pcyls = cylinders; 118 *pheads = 16; 119 *psecs = 63; 120 } 121 122 void hd_geometry_guess(BlockBackend *blk, 123 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs, 124 int *ptrans) 125 { 126 int cylinders, heads, secs, translation; 127 HDGeometry geo; 128 129 /* Try to probe the backing device geometry, otherwise fallback 130 to the old logic. (as of 12/2014 probing only succeeds on DASDs) */ 131 if (blk_probe_geometry(blk, &geo) == 0) { 132 *pcyls = geo.cylinders; 133 *psecs = geo.sectors; 134 *pheads = geo.heads; 135 translation = BIOS_ATA_TRANSLATION_NONE; 136 } else if (guess_disk_lchs(blk, &cylinders, &heads, &secs) < 0) { 137 /* no LCHS guess: use a standard physical disk geometry */ 138 guess_chs_for_size(blk, pcyls, pheads, psecs); 139 translation = hd_bios_chs_auto_trans(*pcyls, *pheads, *psecs); 140 } else if (heads > 16) { 141 /* LCHS guess with heads > 16 means that a BIOS LBA 142 translation was active, so a standard physical disk 143 geometry is OK */ 144 guess_chs_for_size(blk, pcyls, pheads, psecs); 145 translation = *pcyls * *pheads <= 131072 146 ? BIOS_ATA_TRANSLATION_LARGE 147 : BIOS_ATA_TRANSLATION_LBA; 148 } else { 149 /* LCHS guess with heads <= 16: use as physical geometry */ 150 *pcyls = cylinders; 151 *pheads = heads; 152 *psecs = secs; 153 /* disable any translation to be in sync with 154 the logical geometry */ 155 translation = BIOS_ATA_TRANSLATION_NONE; 156 } 157 if (ptrans) { 158 *ptrans = translation; 159 } 160 trace_hd_geometry_guess(blk, *pcyls, *pheads, *psecs, translation); 161 } 162 163 int hd_bios_chs_auto_trans(uint32_t cyls, uint32_t heads, uint32_t secs) 164 { 165 return cyls <= 1024 && heads <= 16 && secs <= 63 166 ? BIOS_ATA_TRANSLATION_NONE 167 : BIOS_ATA_TRANSLATION_LBA; 168 } 169