VIMAGE + PF crash in mbuf destructor

Marko Zec zec at fer.hr
Mon Jul 22 21:38:12 UTC 2013


On Monday 22 July 2013 21:01:31 Adrian Chadd wrote:
> Well I'm worried about _other_ stuff causing issues here.
>
> So - what's the "right" behaviour? Does vnet/vimage make the
> assumption that for all the mbuf processing/free operations, the vnet
> tag/state is set?

To the best of my knowledge, there's nothing vnet-specific in any of the 
mbuf-handling routines, i.e. they should all work fine on a VIMAGE kernel 
even if curvnet isn't set.

My original motivation behind keeping separate UMA zones for each vnet was 
solely to capture resource leaks between vnets in the early days of VIMAGE 
prototyping.  Nothing prevents a single UMA zone to be shared by multiple 
vnets, unless we want to enforce per-vnet limitations on the number of 
items in a zone.

Marko


>
> -adrian
>
> On 22 July 2013 11:59, Craig Rodrigues <rodrigc at freebsd.org> wrote:
> > On Mon, Jul 22, 2013 at 10:11 AM, Adrian Chadd <adrian at freebsd.org> 
wrote:
> >> I don't think the default vnet context is the correct behaviour there.
> >> We'd need to figure out what the vnet context of the mbuf is and set
> >> that.
> >
> > What do you think about Marko's suggestion to de-virtualize
> > V_pf_mtag_z?  What would be the down side of that?
> >
> > I don't understand enough of the PF code to understand which variables
> > need to
> > be virtual and which don't.
> >
> > --
> > Craig
>
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