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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: |
Fri, 14 Jun 2019 06:43:10 +0200 |
User-agent: |
NeoMutt/20180716 |
Hi,
> Can there be a guest that will fail the MBR in such a way? Yes.
> Look at the following MBR partition table of a Windows XP guest in our
> production
> environment:
>
> Disk size in sectors: 16777216
>
> Binary (only one partition 16 bytes): 80 01 01 00 07 fe ff ff 3f 00 00 00 d5
> ea ff 00
> Start: (0, 1, 1, 63)
> End: (1023, 254, 63, 16771859)
>
> As can be easily seen, any MBR guessing algorithm should guess:
>
> 255 heads (since a value of 254 appears), 63 spt (since a value of 63
> appears)
>
> Turns out that this image does not work with 255, 63 but actually requires
>
> 16 heads, 63 spt
>
> to boot.
>
> So relying on MBR partitions alone is not always enough and sometimes manual
> intervention
> is required.
Ok, given that seabios has no setup any manual configuration needs to be done
via qemu.
But why do we need a new interface for that? IDE can pass the geometry
to the guest. virtio-blk has support too (VIRTIO_BLK_F_GEOMETRY).
Likewise scsi (MODE_PAGE_HD_GEOMETRY). So this should be doable without
any qemu changes.
cheers,
Gerd
- [Qemu-block] [QEMU] [PATCH v2 3/8] bootdevice: Add interface to gather LCHS, (continued)
- [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, 2019/06/12
- 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 <=
- 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
Re: [Qemu-block] [SeaBIOS] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface, no-reply, 2019/06/12