On Wed, Jun 19, 2019 at 12:29:04PM +0300, Sam Eiderman wrote: > 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.heub...@oracle.com> > Reviewed-by: Arbel Moshe <arbel.mo...@oracle.com> > Signed-off-by: Sam Eiderman <shmuel.eider...@oracle.com> > --- > bootdevice.c | 32 ++++++++++++++++++++++++++++++++ > hw/nvram/fw_cfg.c | 14 +++++++++++--- > include/sysemu/sysemu.h | 1 + > 3 files changed, 44 insertions(+), 3 deletions(-) > > diff --git a/bootdevice.c b/bootdevice.c > index 2b12fb85a4..b034ad7bdc 100644 > --- a/bootdevice.c > +++ b/bootdevice.c > @@ -405,3 +405,35 @@ void del_boot_device_lchs(DeviceState *dev, const char > *suffix) > } > } > } > + > +/* Serialized as: (device name\0 + lchs struct) x devices */
Comment is outdated. > + 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); Can fw_cfg_modify_file handle buf == NULL? cheers, Gerd