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Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interfac
From: |
Gerd Hoffmann |
Subject: |
Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface |
Date: |
Wed, 12 Jun 2019 15:06:50 +0200 |
User-agent: |
NeoMutt/20180716 |
On Wed, Jun 12, 2019 at 02:59:31PM +0300, Sam Eiderman 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.
--verbose please.
As far I know seabios switches to LBA mode when the disk is simply too
big for LCHS addressing. So I fail to see which problem is solved by
this. If your guest needs LCHS, why do you assign a disk which can't
be fully accessed using LCHS addressing?
> 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.
Well, not really. Moving disks from one controller to another when the
OS depends on LHCS addressing never is a good idea. That already caused
problems in the 90-ies, when moving scsi disks from one scsi host
adapter to another type, *way* before virtualization became a thing.
BTW: One possible way to figure which LCHS layout a disk uses is to
check the MBR partition table. With that we (a) don't need a new
interface between qemu and seabios and (b) it is not needed to manually
specify the geometry.
cheers,
Gerd
- Re: [Qemu-block] [Qemu-devel] [QEMU] [PATCH v2 7/8] bootdevice: FW_CFG interface for LCHS values, (continued)
[Qemu-block] [QEMU] [PATCH v2 4/8] scsi: Propagate unrealize() callback to scsi-hd, Sam Eiderman, 2019/06/12
[Qemu-block] [QEMU] [PATCH v2 2/8] block: Support providing LCHS from user, Sam Eiderman, 2019/06/12
[Qemu-block] [QEMU] [PATCH v2 5/8] bootdevice: Gather LCHS from all relevant devices, Sam Eiderman, 2019/06/12
[Qemu-block] [QEMU] [PATCH v2 8/8] hd-geo-test: Add tests for lchs override, Sam Eiderman, 2019/06/12
[Qemu-block] [QEMU] [PATCH v2 3/8] bootdevice: Add interface to gather LCHS, Sam Eiderman, 2019/06/12
[Qemu-block] [QEMU] [PATCH v2 1/8] block: Refactor macros - fix tabbing, Sam Eiderman, 2019/06/12
Re: [Qemu-block] [SeaBIOS] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, no-reply, 2019/06/12
Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface,
Gerd Hoffmann <=
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Sam Eiderman, 2019/06/12
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Gerd Hoffmann, 2019/06/12
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Sam Eiderman, 2019/06/13
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Sam Eiderman, 2019/06/13
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Gerd Hoffmann, 2019/06/13
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Sam Eiderman, 2019/06/13
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Gerd Hoffmann, 2019/06/14
- Re: [Qemu-block] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Sam Eiderman, 2019/06/14
- Re: [Qemu-block] [Qemu-devel] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Gerd Hoffmann, 2019/06/17
- Re: [Qemu-block] [Qemu-devel] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, Sam Eiderman, 2019/06/17