Re: HVM disc corruption (was Re: Xen won't start its device backend?)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Jun 02, 2015 at 08:50:17PM +0200, Reinoud Zandijk wrote:
> On Tue, Jun 02, 2015 at 06:54:56PM +0200, Manuel Bouyer wrote:
> > Can you try to dump near the end of the disk, instead of near the start ? dd
> > skip=xxx should do it.
> > 
> > If it's a variable overflow somewhere that causes the wrong block to be read
> > this should catch it.
> 
> Yep, i dumped it from block 964200000 (of 964205424) and i did get completely
> different results. Block 8.388.608 (2^32/512) reads in the same so its not an
> overflow i think.
> 
> The error only starts to show between block 250.000.000 (27.89 bits) and block
> 300.000.000 (28.16 bits). And indeed, block 268.435.456 (2^28) maps to sector
> 0 but block 268.435.455 is wrong already.
> 
> Looking at the dmesg, am I right that the piixide in compatibility mode is
> thus resulting in this error since the hvm wd0 uses LBA48 addressing.

Yes, it looks like the IDE emulation in qemu is not working as it should
with LBA48

> 
> As a side notice, the network in hvm is VERY slow most likely due to the
> number of watchdog timeouts i get from re0. Dumping got into the 4kb/sec ;)
> 
> I used
>   vif = [ 'mac=90:e6:ba:6c:6f:d2,bridge=bridge0' ]

You could try to add 'type=ioemu, model=e1000' to the entry above.
I found that the e1000 emulation (wm(4) under NetBSD) gives much better
performances.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--