Re: [Qemu-devel] [PATCH v6 0/8] Add Qemu to SeaBIOS LCHS interface

[Max Reitz]

On 27.08.19 10:24, Sam Eiderman via Qemu-devel wrote:
> v1:
> 
> 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 guess - SeaBIOS, for large enough disks - will
> use LBA translation, which will report 63 SPT instead.
> 
> In addition we can not enforce SeaBIOS to rely on phyiscal geometries at
> all. A virtio-blk-pci virtual disk with 255 phyiscal heads can not
> report more than 16 physical heads when moved to an IDE controller, the
> ATA spec allows a maximum of 16 heads - this is an artifact of
> virtualization.
> 
> By supplying the logical geometies directly we are able to support such
> "exotic" disks.
> 
> We will use fw_cfg to do just that.
> 
> v2:
> 
> Fix missing parenthesis check in
>     "hd-geo-test: Add tests for lchs override"
> 
> v3:
> 
> * Rename fw_cfg key to "bios-geometry".
> * Remove "extendible" interface.
> * Add cpu_to_le32 fix as Laszlo suggested or big endian hosts
> * Fix last qtest commit - automatic docker tester for some reason does not 
> have qemu-img set
> 
> v4:
> 
> * Change fw_cfg interface from mixed textual/binary to textual only
> 
> v5:
> 
> * Fix line > 80 chars in tests/hd-geo-test.c
> 
> v6:
> 
> * Small fixes for issues pointed by Max
> * (&conf->conf)->lcyls to conf->conf.lcyls and so on
> * Remove scsi_unrealize from everything other than scsi-hd
> * Add proper include to sysemu.h
> * scsi_device_unrealize() after scsi_device_purge_requests()
> 
> Sam Eiderman (8):
>   block: Refactor macros - fix tabbing
>   block: Support providing LCHS from user
>   bootdevice: Add interface to gather LCHS
>   scsi: Propagate unrealize() callback to scsi-hd
>   bootdevice: Gather LCHS from all relevant devices
>   bootdevice: Refactor get_boot_devices_list
>   bootdevice: FW_CFG interface for LCHS values
>   hd-geo-test: Add tests for lchs override
> 
>  bootdevice.c             | 148 ++++++++--
>  hw/block/virtio-blk.c    |   6 +
>  hw/ide/qdev.c            |   7 +-
>  hw/nvram/fw_cfg.c        |  14 +-
>  hw/scsi/scsi-bus.c       |  16 ++
>  hw/scsi/scsi-disk.c      |  12 +
>  include/hw/block/block.h |  22 +-
>  include/hw/scsi/scsi.h   |   1 +
>  include/sysemu/sysemu.h  |   4 +
>  tests/Makefile.include   |   2 +-
>  tests/hd-geo-test.c      | 582 +++++++++++++++++++++++++++++++++++++++
>  11 files changed, 773 insertions(+), 41 deletions(-)

Acked-by: Max Reitz <address@hidden>

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