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 "hw/block/block.h"
  36#include "trace.h"
  37
  38struct 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 */
  53static 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
 101static 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
 120void 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
 161int 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}
 167