Re: Out of sync shadow core breaks Hurd

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Nov 12, 2008 at 08:00:37PM +0100, Aurelien Jarno wrote:
> Hi,
> 
> Starting with kvm-76 (and including kvm-79), Hurd does not boot anymore
> under KVM. The ext2fs translator issues a strange error message:
> 
> | Hurd server bootstrap: ext2fs.static[device:hd0s3] execext2fs.static: /build/bui
> | ldd/hurd-20080607/build-tree/hurd/ext2fs/dir.c:494: dirscanblock: Assertion `dp-
> | >dn->dirents[idx] == -1 || dp->dn->dirents[idx] == nentries' failed.           -
> | >dn->dirents[idx] == -1 || dp->dn->dirents[idx] == nentries' failed.
> 
> Bisecting the problem, I have found that it comes from this patch:
> 
> | 641fb03992b20aa640781a245f6b7136f0b845e4 is first bad commit
> | commit 641fb03992b20aa640781a245f6b7136f0b845e4
> | Author: Marcelo Tosatti <mtosatti@redhat.com>
> | Date:   Tue Sep 23 13:18:39 2008 -0300
> | 
> |     KVM: MMU: out of sync shadow core v2
> | 
> |     Allow guest pagetables to go out of sync.
> | 
> |     Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> |     Signed-off-by: Avi Kivity <avi@redhat.com>
> 
> The problem can be workarounded loading the kvm module with 
> oos_shadow=0.
> 
> The easiest way to reproduce the problem is to download a ready to use
> Hurd image [1]. The error message from the ext2fs translator is not
> exactly the same, but it still fails.

Thanks Aurelien, I'll be looking at this next week.