2 * Hard disk geometry utilities
4 * Copyright (C) 2012 Red Hat, Inc.
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.
9 * This file incorporates work covered by the following copyright and
12 * Copyright (c) 2003 Fabrice Bellard
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:
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
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
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33 #include "qemu/osdep.h"
34 #include "sysemu/block-backend.h"
35 #include "hw/block/block.h"
39 uint8_t boot_ind; /* 0x80 - active */
40 uint8_t head; /* starting head */
41 uint8_t sector; /* starting sector */
42 uint8_t cyl; /* starting cylinder */
43 uint8_t sys_ind; /* What partition type */
44 uint8_t end_head; /* end head */
45 uint8_t end_sector; /* end sector */
46 uint8_t end_cyl; /* end cylinder */
47 uint32_t start_sect; /* starting sector counting from 0 */
48 uint32_t nr_sects; /* nr of sectors in partition */
51 /* try to guess the disk logical geometry from the MSDOS partition table.
52 Return 0 if OK, -1 if could not guess */
53 static int guess_disk_lchs(BlockBackend *blk,
54 int *pcylinders, int *pheads, int *psectors)
56 uint8_t buf[BDRV_SECTOR_SIZE];
57 int i, heads, sectors, cylinders;
62 blk_get_geometry(blk, &nb_sectors);
65 * The function will be invoked during startup not only in sync I/O mode,
66 * but also in async I/O mode. So the I/O throttling function has to
67 * be disabled temporarily here, not permanently.
69 if (blk_read_unthrottled(blk, 0, buf, 1) < 0) {
72 /* test msdos magic */
73 if (buf[510] != 0x55 || buf[511] != 0xaa) {
76 for (i = 0; i < 4; i++) {
77 p = ((struct partition *)(buf + 0x1be)) + i;
78 nr_sects = le32_to_cpu(p->nr_sects);
79 if (nr_sects && p->end_head) {
80 /* We make the assumption that the partition terminates on
81 a cylinder boundary */
82 heads = p->end_head + 1;
83 sectors = p->end_sector & 63;
87 cylinders = nb_sectors / (heads * sectors);
88 if (cylinders < 1 || cylinders > 16383) {
93 *pcylinders = cylinders;
94 trace_hd_geometry_lchs_guess(blk, cylinders, heads, sectors);
101 static void guess_chs_for_size(BlockBackend *blk,
102 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs)
107 blk_get_geometry(blk, &nb_sectors);
109 cylinders = nb_sectors / (16 * 63);
110 if (cylinders > 16383) {
112 } else if (cylinders < 2) {
120 void hd_geometry_guess(BlockBackend *blk,
121 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs,
124 int cylinders, heads, secs, translation;
127 /* Try to probe the backing device geometry, otherwise fallback
128 to the old logic. (as of 12/2014 probing only succeeds on DASDs) */
129 if (blk_probe_geometry(blk, &geo) == 0) {
130 *pcyls = geo.cylinders;
131 *psecs = geo.sectors;
133 translation = BIOS_ATA_TRANSLATION_NONE;
134 } else if (guess_disk_lchs(blk, &cylinders, &heads, &secs) < 0) {
135 /* no LCHS guess: use a standard physical disk geometry */
136 guess_chs_for_size(blk, pcyls, pheads, psecs);
137 translation = hd_bios_chs_auto_trans(*pcyls, *pheads, *psecs);
138 } else if (heads > 16) {
139 /* LCHS guess with heads > 16 means that a BIOS LBA
140 translation was active, so a standard physical disk
142 guess_chs_for_size(blk, pcyls, pheads, psecs);
143 translation = *pcyls * *pheads <= 131072
144 ? BIOS_ATA_TRANSLATION_LARGE
145 : BIOS_ATA_TRANSLATION_LBA;
147 /* LCHS guess with heads <= 16: use as physical geometry */
151 /* disable any translation to be in sync with
152 the logical geometry */
153 translation = BIOS_ATA_TRANSLATION_NONE;
156 *ptrans = translation;
158 trace_hd_geometry_guess(blk, *pcyls, *pheads, *psecs, translation);
161 int hd_bios_chs_auto_trans(uint32_t cyls, uint32_t heads, uint32_t secs)
163 return cyls <= 1024 && heads <= 16 && secs <= 63
164 ? BIOS_ATA_TRANSLATION_NONE
165 : BIOS_ATA_TRANSLATION_LBA;