WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

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


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