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Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error.
From: |
Carl-Daniel Hailfinger |
Subject: |
Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error. |
Date: |
Tue, 20 Jan 2009 11:44:57 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.17) Gecko/20080922 SUSE/1.1.12-0.1 SeaMonkey/1.1.12 |
On 20.01.2009 10:35, Gleb Natapov wrote:
> On Tue, Jan 20, 2009 at 10:25:04AM +0100, Gerd Hoffmann wrote:
>
>> Ian Jackson wrote:
>>
>>> Anthony Liguori writes ("Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC
>>> error."):
>>>
>>>> Ian Jackson wrote:
>>>>
>>>>> Once again, this feature should be optional.
>>>>>
>>>> Why?
>>>>
>>> Well, three reasons, one general and theoretical, and two practical
>>> and rather Xen-specific.
>>>
>>> The theoretical reason is that a guest is in a better postion to deal
>>> with the situation because it knows its access patterns. Often the
>>> response to a failing write in a mission-critical system will be some
>>> kind a fallback behaviour, which is likely to work. Stopping the VM
>>> unconditionally is not something that the guest can cope with.
>>>
>> The fundamental issue is that you can't signal ENOSPC to the guest via
>> IDE protocol because that is an error condition which simply can't
>> happen on real hardware. You can only signal EIO, which is something
>> very different, and the OS likely goes into "Oops, disk broken" mode.
>> Which probably isn't what you want here ...
>>
>>
> Windows using IDE retries DMA 3 times and then moves to PIO mode. And it
> stays in PIO mode even after reboot. The only way to return to DMA mode
> again is to reinstall the driver.
>
You can fix this in the registry without any reinstallation by setting
the bitmask of allowed IDE modes back to 0xffffffff. It's a single value
that needs to be changed. http://winhlp.com/node/10 has more info and a
script to reset the bitmask.
There's also an alternative for automatically resetting the mode after a
successful access: http://support.microsoft.com/kb/817472
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
- [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Gleb Natapov, 2009/01/18
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Ian Jackson, 2009/01/19
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Gleb Natapov, 2009/01/19
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Anthony Liguori, 2009/01/19
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Ian Jackson, 2009/01/19
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Avi Kivity, 2009/01/19
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Gleb Natapov, 2009/01/19
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Gerd Hoffmann, 2009/01/20
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Gleb Natapov, 2009/01/20
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error.,
Carl-Daniel Hailfinger <=
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Gleb Natapov, 2009/01/20
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Vincent Hanquez, 2009/01/20