Re: Data corruption in guest using KVM

Aurelien Jarno
2007-07-23T06:08:27Z

On Mon, Jul 23, 2007 at 01:34:29AM +0200, Aurelien Jarno wrote:
> On Sun, Jul 22, 2007 at 08:34:37PM +0300, Avi Kivity wrote:
> > Aurelien Jarno wrote:
> > > On Sun, Jul 22, 2007 at 04:46:19PM +0300, Avi Kivity wrote:
> > >
> > >> If you do happen to get a same-size corruption, that may tell us more.
> > >>
> > >>
> > >
> > > I have just got one same-size corruption building glibc 2.6 on
> > > GNU/kFreeBSD i386 (32-bit nonpae).
> > >
> > > One byte at address 0x9000 has been replaced by 0x00. Please find the
> > > good and the bad file attached.
> > >
> > >
> >
> > Good. We have one or two cross-page-boundary bugs. The
> > corruption-chase branch already fixes one (which is much more likely to
> > be triggered by FreeBSD than Linux, if I understand the FreeBSD VM
> > correctly).
> >
>
> I have tried this branch, and the data get corrupted another way. This
> is due to the fact that the source address is not incremented for the
> second write. The patch below fixes that.
>
> With this patch, I haven't be able to make any corruption. I have added
> a printk in the code to see that I have been able to trigger 21
> cross-boundary writes without any problem in the various guests.
>

After a night of tests, 172 cross-boundary writes have been triggered,
still nothing wrong in the guests.

--
.''`. Aurelien Jarno | GPG: 1024D/F1BCDB73
: :' : Debian developer | Electrical Engineer
`. `' aurel32-8fiUuRrzOP0dnm+yROfE0A@public.gmane.org | aurelien-rXXEIb44qovR7s880joybQ@public.gmane.org
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