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 "hw/block/block.h"
  36 #include "trace.h"
  37
  38 struct partition {
  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 */
  49 } QEMU_PACKED;
  50
  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)
  55 {
  56     uint8_t buf[BDRV_SECTOR_SIZE];
  57     int i, heads, sectors, cylinders;
  58     struct partition *p;
  59     uint32_t nr_sects;
  60     uint64_t nb_sectors;
  61
  62     blk_get_geometry(blk, &nb_sectors);
  63
  64     /**
  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.
  68      */
  69     if (blk_read_unthrottled(blk, 0, buf, 1) < 0) {
  70         return -1;
  71     }
  72     /* test msdos magic */
  73     if (buf[510] != 0x55 || buf[511] != 0xaa) {
  74         return -1;
  75     }
  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;
  84             if (sectors == 0) {
  85                 continue;
  86             }
  87             cylinders = nb_sectors / (heads * sectors);
  88             if (cylinders < 1 || cylinders > 16383) {
  89                 continue;
  90             }
  91             *pheads = heads;
  92             *psectors = sectors;
  93             *pcylinders = cylinders;
  94             trace_hd_geometry_lchs_guess(blk, cylinders, heads, sectors);
  95             return 0;
  96         }
  97     }
  98     return -1;
  99 }
 100
 101 static void guess_chs_for_size(BlockBackend *blk,
 102                 uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs)
 103 {
 104     uint64_t nb_sectors;
 105     int cylinders;
 106
 107     blk_get_geometry(blk, &nb_sectors);
 108
 109     cylinders = nb_sectors / (16 * 63);
 110     if (cylinders > 16383) {
 111         cylinders = 16383;
 112     } else if (cylinders < 2) {
 113         cylinders = 2;
 114     }
 115     *pcyls = cylinders;
 116     *pheads = 16;
 117     *psecs = 63;
 118 }
 119
 120 void hd_geometry_guess(BlockBackend *blk,
 121                        uint32_t *pcyls, uint32_t *pheads, uint32_t *psecs,
 122                        int *ptrans)
 123 {
 124     int cylinders, heads, secs, translation;
 125     HDGeometry geo;
 126
 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;
 132         *pheads = geo.heads;
 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
 141            geometry is OK */
 142         guess_chs_for_size(blk, pcyls, pheads, psecs);
 143         translation = *pcyls * *pheads <= 131072
 144             ? BIOS_ATA_TRANSLATION_LARGE
 145             : BIOS_ATA_TRANSLATION_LBA;
 146     } else {
 147         /* LCHS guess with heads <= 16: use as physical geometry */
 148         *pcyls = cylinders;
 149         *pheads = heads;
 150         *psecs = secs;
 151         /* disable any translation to be in sync with
 152            the logical geometry */
 153         translation = BIOS_ATA_TRANSLATION_NONE;
 154     }
 155     if (ptrans) {
 156         *ptrans = translation;
 157     }
 158     trace_hd_geometry_guess(blk, *pcyls, *pheads, *psecs, translation);
 159 }
 160
 161 int hd_bios_chs_auto_trans(uint32_t cyls, uint32_t heads, uint32_t secs)
 162 {
 163     return cyls <= 1024 && heads <= 16 && secs <= 63
 164         ? BIOS_ATA_TRANSLATION_NONE
 165         : BIOS_ATA_TRANSLATION_LBA;
 166 }