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: Karl Heubaum <karl.heubaum@oracle.com>
Reviewed-by: Arbel Moshe <arbel.moshe@oracle.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Sam Eiderman <shmuel.eiderman@oracle.com>
Signed-off-by: Sam Eiderman <sameid@google.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
Sam Eiderman 2019-10-16 19:41:44 +03:00 committed by John Snow
parent 42f0680199
commit aea60a13b9
3 changed files with 43 additions and 3 deletions

View File

@ -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;
}

View File

@ -949,13 +949,21 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
static void fw_cfg_machine_reset(void *opaque) static void fw_cfg_machine_reset(void *opaque)
{ {
MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
FWCfgState *s = opaque;
void *ptr; void *ptr;
size_t len; size_t len;
FWCfgState *s = opaque; char *buf;
char *bootindex = get_boot_devices_list(&len);
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); 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) static void fw_cfg_machine_ready(struct Notifier *n, void *data)

View File

@ -106,6 +106,7 @@ void validate_bootdevices(const char *devices, Error **errp);
void add_boot_device_lchs(DeviceState *dev, const char *suffix, void add_boot_device_lchs(DeviceState *dev, const char *suffix,
uint32_t lcyls, uint32_t lheads, uint32_t lsecs); uint32_t lcyls, uint32_t lheads, uint32_t lsecs);
void del_boot_device_lchs(DeviceState *dev, const char *suffix); 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 */ /* handler to set the boot_device order for a specific type of MachineClass */
typedef void QEMUBootSetHandler(void *opaque, const char *boot_order, typedef void QEMUBootSetHandler(void *opaque, const char *boot_order,