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SubjectRe: Checkin 7404ad3b6d04efbd918e9e2e776bf560fbedf47d breaks boot on KVM
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On Mon, 2008-10-13 at 17:03 -0700, H. Peter Anvin wrote:
> I just tried a top of tree i386 kernel under KVM, and found that it
> fails to boot with a hang during initialization, right after:
>
> console [netcon0] enabled
>
> netconsole: network logging started
>
> Uniform Multi-Platform E-IDE driver
>
> ide-floppy driver 1.00
>
> Driver 'sd' needs updating - please use bus_type methods
>
> scsi0 : ata_piix
>
> scsi1 : ata_piix
>
> ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc000 irq 14
>
> ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc008 irq 15
>
> ata1.00: ATA-7: QEMU HARDDISK, 0.9.1, max UDMA/100
>
> ata1.00: 16777216 sectors, multi 16: LBA48
>
> ata1.00: configured for MWDMA2
>
> ata2.00: ATAPI: QEMU DVD-ROM, 0.9.1, max UDMA/100
>
> ata2.00: configured for MWDMA2
>
> scsi 0:0:0:0: Direct-Access ATA QEMU HARDDISK 0.9. PQ: 0
> ANSI: 5
>
> Bisection fingered the following commit:
>
> 7404ad3b6d04efbd918e9e2e776bf560fbedf47d is first bad commit
>
> commit 7404ad3b6d04efbd918e9e2e776bf560fbedf47d
>
> Author: James Bottomley <James.Bottomley@HansenPartnership.com>
>
> Date: Sun Aug 31 10:41:52 2008 -0500
>
>
> [SCSI] sd: use generic helper to print capacities in both binary
> and SI
>
> Signed-off-by: James Bottomley
> <James.Bottomley@HansenPartnership.com>
>
> :040000 040000 98fc7ae95211b8d16e2e8ca46997be660ad9ba93
> 2d35d0a2b6232411b840a9ccf6a52b946172566e M drivers
>
> However, simply reverting this commit caused a panic on boot (not
> entirely surprising.)

Actually, it is surprising. That patch takes the default arithmetic for
calculating the disk size out of sd and uses a routine to do it more
efficiently in lib/string_helpers.c

So there are two problems: Why does it panic on revert (could you post
the oops) and what does kvm object to in string_get_size ... it's a
fairly innocuous routine as I read it ... your symptoms sound like the
for loop isn't terminating.

James




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