hw/block/hd-geometry.c

   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 }