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