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kdump on linux on Hyper-V RRS feed

  • Question

  • Hi experts,

    I am running a custom Linux VM on Hyper-V 2008 R2. I have Linux Integration Services 3.4 installed. I have two disks configured. One IDE boot disk (4GB) and another SCSI data disk (80GB).

    Since kdump is not supported on Linux guests, I made the workaround given in the below post.

    http://support.microsoft.com/kb/2858695/en-us

    But I am getting into kernel panic every time I run the sysrq kdump.  MS didn't say anything about the support of Hyper-V in ata_piix driver.

    I checked the Linux ata_piix driver code and found some additions. So I added those additions in my kernel. But when I build with those changes, I am getting compilation errors.

    Questions:

    1.Is the above MS workaround fine?

    2.What about the ata_piix modifications ?

    Thanks in advance,

    Salim

    • Moved by BrianEhMVP Tuesday, January 28, 2014 4:09 PM
    Tuesday, January 28, 2014 2:55 PM

All replies

  • Hi Salim,

    The workarounds mentioned in the kb article are accurate. Can you post a screenshot from the kernel panic? That way we might be able to provide some insight in to why it is not working. ata_piix is the legacy storage driver and should just work with Hyper-V without further enhancements. You might want to investigate the root cause of the panic.

    Thanks,

    Abhishek


    Wednesday, January 29, 2014 3:57 AM
  • Thanks Abhishek.

    But, the code to use ata_piix driver during crash is not present in my kernel.

    I have added those changes from ata_piix code.

    Thanks,

    Salimm

    Friday, March 28, 2014 2:03 PM
  • Hi Saleem, It is hard for me to debug this without having access to your setup. However what I can tell you is that you need to ensure that the Hyper-V drivers and the ata_piix driver needs to be available in the initird for the kexec kernel. Have you included all the requisite drivers for the kexec kernel? Please let me know.

    Thanks,

    Abhishek

    Thursday, April 3, 2014 8:38 PM
  • After analysis, I found that that ata_piix driver cannot identify my SCSI disk. But the IDE disk is identified by ata_piix only. The SCSI Emulation in Hyper-V does not list the SCSI disk externally. (#lspci does not show it).

    [    0.159984] libata version 3.00 loaded.
    [    6.233022] ata_piix 0000:00:07.1: version 2.13
    [    6.233022] ata_piix 0000:00:07.1: setting latency timer to 64
    [    6.234286] scsi0 : ata_piix
    [    6.234286] scsi1 : ata_piix
    [    6.236020] ata1: PATA max UDMA/33 cmd 0x1f0 ctl 0x3f6 bmdma 0xffa0 irq 14
    [    6.236020] ata2: PATA max UDMA/33 cmd 0x170 ctl 0x376 bmdma 0xffa8 irq 15
    [    6.389014] ata1.00: ATA-8: Virtual HD, 1.1.0, max MWDMA2
    [    6.389014] ata1.00: 8388608 sectors, multi 128: LBA48
    [    6.390071] ata2.00: ATAPI: Virtual CD, , max MWDMA2
    [    6.391186] ata1.00: configured for MWDMA2
    [    6.392059] ata2.00: configured for MWDMA2
    [    6.651020] trackpoint.c: failed to get extended button data
    [   35.057013] EXT3-fs: mounted filesystem with ordered data mode.

    bash-3.2#
    bash-3.2#dmesg | grep storvsc
    [   12.046020] hv_vmbus: registering driver hv_storvsc
    [   12.059518] scsi2 : storvsc_host_t

    Is there any way I can make ata_piix identify the SCSI disk, so the MSFT workaround works for me?

    Thanks,

    Saleem

    Monday, April 7, 2014 10:31 AM
  • Hi Saleem,

    Have you successfully specified the prefer_ms_hyper_v as 0 for the kexec kernel? You need to include changes related to this parameter as well. As mentioned in the KB article, this parameter is used to enable or disable the storvsc driver. If the storvsc driver is disabled then you should be able to access the SCSI drives using the ata_piix driver automatically. Let me know if you can see the prefer_ms_hyper_v flag as disabled while running your ata_piix driver.

    Thanks,

    Abhishek

    Monday, April 7, 2014 9:13 PM
  • I have made the necessary changes as per the KB article.

    I have disabled storvsc. But the ata_piix driver is unable to detect the SCSI drives.

    The SCSI drives are not detected as PCI devices as well.

    It is metioned in the link

    http://blogs.msdn.com/b/virtual_pc_guy/archive/2009/12/01/why-hyper-v-cannot-boot-off-of-scsi-disks-and-why-you-should-not-care.aspx

    Are you sure that the ata_piix driver in the kernel is able to  access the SCSI drives?

    IS MSFT have done any tests with it?

    Thanks,

    Saleem


    • Edited by A Saleem Wednesday, April 9, 2014 2:35 PM
    Wednesday, April 9, 2014 5:38 AM
  • Hi Saleem, I apologize for incorrectly suggesting that ATA driver can access SCSI devices. ATA driver cannot access SCSI devices and therefore you will have to configure kexec kernel to dump core to your IDE devices. Let me know if you have further questions.

    Thanks,
    Abhishek

    Saturday, April 12, 2014 12:06 AM