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Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error.
From: |
Gleb Natapov |
Subject: |
Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error. |
Date: |
Tue, 20 Jan 2009 11:35:40 +0200 |
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.
--
Gleb.
- [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 <=
- Re: [Qemu-devel] [PATCH v3] Stop VM on ENOSPC error., Carl-Daniel Hailfinger, 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., Vincent Hanquez, 2009/01/20