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

[Derek Glidden <dglidden@xxxxxxxxxxxxxxx>]

On Jul 23, 2004, at 12:01 PM, Keir Fraser wrote:

> Okay, so I found that the problem is due to overly-aggressive merging
> of block requests in the IDE driver. The code assumes that if buffers
> are adjacent in virtual or physical address space then they can be
> merged --- this isn't always the case over Xen since those physical
> addresses may map to different real machine pages.
And there was much rejoicing!

Thanks Keir for working so hard on digging this problem out and getting 
a fix in.
Other than the doms not dying after a halt, which you said you checked 
in a fix, and the occasional strange unbalanced dom scheduling, which I 
understand the scheduler is being worked on, the -unstable branch has 
worked very well for me so far.  (Well, outside of the random 
crashes... :)
I'll do a pull tonight when I get home and rebuild everything and start 
hammering on it some more.
> 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?
> 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?
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
"I think that's what they mean by   |
"nickels a day can feed a child."   |       http://www.eff.org/
I thought, "How can food be so      | http://www.anti-dmca.org/
cheap over there?"  It's not, they  |--------------------------
just eat the nickels." -- Peter Nguyen


-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
"We all enter this world in the    | Support Electronic Freedom
same way: naked; screaming; soaked |        http://www.eff.org/
in blood. But if you live your     |  http://www.anti-dmca.org/
life right, that kind of thing     |---------------------------
doesn't have to stop there." -- Dana Gould



-------------------------------------------------------
This SF.Net email is sponsored by BEA Weblogic Workshop
FREE Java Enterprise J2EE developer tools!
Get your free copy of BEA WebLogic Workshop 8.1 today.
http://ads.osdn.com/?ad_id=4721&alloc_id=10040&op=click
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.sourceforge.net/lists/listinfo/xen-devel