Re: [Xen-devel] [PATCH 2/3 v3] Refactor MSI restore call-chain todrop unnecessary argument

[Zhenzhong Duan]

On 2013-08-29 15:23, Jan Beulich wrote:
> > > > On 29.08.13 at 04:52, Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx> wrote:
> > But in initial domain (aka priviliged guest), it's different.
> > Driver init call graph under initial domain:
> > driver_init->
> >      msix_capability_init->
> >          msix_program_entries->
> >              msix_mask_irq->
> >                  entry->masked = 1
> >      request_irq->
> >          __setup_irq->
> >              irq_startup->
> >                  __startup_pirq->
> >                      EVTCHNOP_bind_pirq hypercall    (trap into Xen)
> > [Xen:]
> > pirq_guest_bind->
> >      startup_msi_irq->
> >          unmask_msi_irq->
> >              msi_set_mask_bit->
> >                  entry->msi_attrib.masked = 0
> >
> > So entry->msi_attrib.masked in xen side always has newest value. entry->masked
> > in initial domain is untouched and is 1 after msix_capability_init.
> And as said several times before - Linux shouldn't be touching
> the MSI-X table at all during initial setup or resume (it should in
> particular not rely on such accesses to not fault, as being a
> privilege violation); all it needs to do is update its software state.
My patch just remove access to msix mask register in dom0. Anything 
wrong with that?
> Hence fiddling with default_restore_msi_irqs() seems the wrong
> approach towards solving the problem.
dom0 uses xen_initdom_restore_msi_irqs, default_restore_msi_irqs is for 
baremetal.

zduan
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