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 "qapi/qapi-types-block.h"
  36#include "qemu/bswap.h"
  37#include "hw/block/block.h"
  38#include "trace.h"
  39
  40struct 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 */
  55static 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
 103static 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
 122void 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
 163int 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