Re: [Xen-devel] [PATCH QEMU v2] xen/pt: allow QEMU to request MSI unmasking at bind time

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

On Thu, Aug 24, 2017 at 07:09:08AM -0600, Jan Beulich wrote:
> >>> On 24.08.17 at 14:19, <roger.pau@xxxxxxxxxx> wrote:
> > When a MSI interrupt is bound to a guest using
> > xc_domain_update_msi_irq (XEN_DOMCTL_bind_pt_irq) the interrupt is
> > left masked by default.
> > 
> > This causes problems with guests that first configure interrupts and
> > clean the per-entry MSIX table mask bit and afterwards enable MSIX
> > globally. In such scenario the Xen internal msixtbl handlers would not
> > detect the unmasking of MSIX entries because vectors are not yet
> > registered since MSIX is not enabled, and vectors would be left
> > masked.
> > 
> > Introduce a new flag in the gflags field to signal Xen whether a MSI
> > interrupt should be unmasked after being bound.
> > 
> > This also requires to track the mask register for MSI interrupts, so
> > QEMU can also notify to Xen whether the MSI interrupt should be bound
> > masked or unmasked
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > Reported-by: Andreas Kinzler <hfp@xxxxxxxxx>
> 
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Thanks, Roger.

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