Commit aea60a13 authored by Sam Eiderman's avatar Sam Eiderman Committed by John Snow
Browse files

bootdevice: FW_CFG interface for LCHS values 



Using fw_cfg, supply logical CHS values directly from QEMU to the BIOS.

Non-standard logical geometries break under QEMU.

A virtual disk which contains an operating system which depends on
logical geometries (consistent values being reported from BIOS INT13
AH=08) will most likely break under QEMU/SeaBIOS if it has non-standard
logical geometries - for example 56 SPT (sectors per track).
No matter what QEMU will report - SeaBIOS, for large enough disks - will
use LBA translation, which will report 63 SPT instead.

In addition we cannot force SeaBIOS to rely on physical geometries at
all. A virtio-blk-pci virtual disk with 255 phyiscal heads cannot
report more than 16 physical heads when moved to an IDE controller,
since the ATA spec allows a maximum of 16 heads - this is an artifact of
virtualization.

By supplying the logical geometries directly we are able to support such
"exotic" disks.

We serialize this information in a similar way to the "bootorder"
interface.
The new fw_cfg entry is "bios-geometry".

Reviewed-by: default avatarKarl Heubaum <karl.heubaum@oracle.com>
Reviewed-by: default avatarArbel Moshe <arbel.moshe@oracle.com>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: default avatarSam Eiderman <shmuel.eiderman@oracle.com>
Signed-off-by: default avatarSam Eiderman <sameid@google.com>
Tested-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: default avatarJohn Snow <jsnow@redhat.com>
parent 42f06801

bootdevice.c

+31 −0
Original line number Diff line number Diff line
@@ -405,3 +405,34 @@ void del_boot_device_lchs(DeviceState *dev, const char *suffix) 
        }

    }

}



char *get_boot_devices_lchs_list(size_t *size)

{

    FWLCHSEntry *i;

    size_t total = 0;

    char *list = NULL;



    QTAILQ_FOREACH(i, &fw_lchs, link) {

        char *bootpath;

        char *chs_string;

        size_t len;



        bootpath = get_boot_device_path(i->dev, false, i->suffix);

        chs_string = g_strdup_printf("%s %" PRIu32 " %" PRIu32 " %" PRIu32,

                                     bootpath, i->lcyls, i->lheads, i->lsecs);



        if (total) {

            list[total - 1] = '\n';

        }

        len = strlen(chs_string) + 1;

        list = g_realloc(list, total + len);

        memcpy(&list[total], chs_string, len);

        total += len;

        g_free(chs_string);

        g_free(bootpath);

    }



    *size = total;



    return list;

}

hw/nvram/fw_cfg.c

+11 −3
Original line number Diff line number Diff line
@@ -949,13 +949,21 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename, 


static void fw_cfg_machine_reset(void *opaque)

{

    MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());

    FWCfgState *s = opaque;

    void *ptr;

    size_t len;

    FWCfgState *s = opaque;

    char *bootindex = get_boot_devices_list(&len);

    char *buf;



    ptr = fw_cfg_modify_file(s, "bootorder", (uint8_t *)bootindex, len);

    buf = get_boot_devices_list(&len);

    ptr = fw_cfg_modify_file(s, "bootorder", (uint8_t *)buf, len);

    g_free(ptr);



    if (!mc->legacy_fw_cfg_order) {

        buf = get_boot_devices_lchs_list(&len);

        ptr = fw_cfg_modify_file(s, "bios-geometry", (uint8_t *)buf, len);

        g_free(ptr);

    }

}



static void fw_cfg_machine_ready(struct Notifier *n, void *data)

include/sysemu/sysemu.h

+1 −0
Original line number Diff line number Diff line
@@ -106,6 +106,7 @@ void validate_bootdevices(const char *devices, Error **errp); 
void add_boot_device_lchs(DeviceState *dev, const char *suffix,

                          uint32_t lcyls, uint32_t lheads, uint32_t lsecs);

void del_boot_device_lchs(DeviceState *dev, const char *suffix);

char *get_boot_devices_lchs_list(size_t *size);



/* handler to set the boot_device order for a specific type of MachineClass */

typedef void QEMUBootSetHandler(void *opaque, const char *boot_order,