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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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.

Hence fiddling with default_restore_msi_irqs() seems the wrong
approach towards solving the problem.

Jan


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