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Re: [Xen-devel] segfault in VM - FIXED!

To: Derek Glidden <dglidden@xxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] segfault in VM - FIXED!
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 23 Jul 2004 18:55:00 +0100
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> > I've checked in a fix that I think is safe for IDE --- in the
> > occasional instances that a merged scatter-gather list is invalid, we
> > should now cause IDE to fall back to a super-safe mode (basically
> > PIO). On my system this happens so occasionally that performance
> > shouldn't be affected.
> Does it revert back to "normal" behaviour for consequent operations?  
> i.e. is the "basically PIO" mode just for the operation that fails?

That is correct -- in practice very very few requests should end up
using PIO.

> > What we need now is some more checking, particularly with SCSI block
> > devices, to see whether there are any more bugs to shake out.
> Would it help at all for me to set up a box as ide-scsi, or is it 
> strictly the data path inside the individual SCSI drivers that could 
> cause problems?

Stress-testing in as many environments and setups as possible is very

I've also contacted the linux-kernel mailing list to find out whether
anyone there has a btter fix, or would be amenable to some
Xen-friendly patches being sent their way. ;-)

 -- Keir

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