Re: [Xen-devel] [PATCH] fix XSA-46 regression with xend/xm

[Gordan Bobic <gordan@xxxxxxxxxx>]

On Tue, 21 May 2013 09:56:27 +0100, Ian Campbell 
<Ian.Campbell@xxxxxxxxxx> wrote:
> On Tue, 2013-05-21 at 09:40 +0100, Jan Beulich wrote:
> > The hypervisor side changes for XSA-46 require the tool stack to now
> > always map the guest pIRQ before granting access permission to the
> > underlying host IRQ (GSI). This in particular requires that pciif.py
> > no longer can skip this step (assuming qemu would do it) for HVM
> > guests.
> >
> > This in turn exposes, however, an inconsistency between xend and 
> > qemu:
> > The former wants to always establish 1:1 mappings between pIRQ and 
> > host
> > IRQ (for non-MSI only of course), while the latter always wants to
> > allocate an arbitrary mapping. Since the whole tool stack obviously
> > should always agree on the mapping model, make libxc enforce the 1:1
> > mapping as the more natural one (as well as being the one that 
> > allows
> > for easier debugging, since there no need to find out the extra
> > mapping). Users of libxc that want to establish a particular (rather
> > than an allocated) mapping are still free to do so, as well as tool
> > stacks not based on libxc wanting to implement an allocation based
> > model (which is why it's not the hypervisor that's being changed to
> > enforce either model).
> >
> > Since libxl, like xend, already uses a 1:1 model, it's unaffected by
> > the libxc change (and it being unaffected by the original hypervisor
> > side changes is - afaict - simply due to qemu getting spawned at a
> > later point in time compared to the xend event flow).
> >
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > Tested-by: Andreas Falck <falck.andreas.lists@xxxxxxxxx> (on 4.1)
> > Tested-by: Gordan Bobic <gordan@xxxxxxxxxx> (on 4.2)
> In both cases tested with xend rather than xl or both?
My tests were done using xm only. I never tried xl so don't know if
it was affected in the first place. I will try xl tonight to verify
that it works.

Gordan

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