Re: [PATCH v2] PCI: vmd: Offset Client VMD MSI/X vectors

["Derrick, Jonathan" <jonathan.derrick@intel.com>]

On Tue, 2020-09-15 at 03:42 +0900, Keith Busch wrote:
> On Mon, Sep 14, 2020 at 01:32:55PM -0400, Jon Derrick wrote:
> > Client VMD platforms have a software-triggered MSI/X vector 0 that will
> > not forward hardware-remapped MSI/X vectors from the sub-device domain.
> > This causes an issue with VMD platforms that use AHCI behind VMD and
> > have a single MSI/X vector mapping to vector 0. Add an MSI/X vector
> > offset for these platforms.
> > 
> > Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
> > ---
> >  drivers/pci/controller/vmd.c | 35 +++++++++++++++++++++++++----------
> >  1 file changed, 25 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> > index f69ef8c89f72..f8195bad79d1 100644
> > --- a/drivers/pci/controller/vmd.c
> > +++ b/drivers/pci/controller/vmd.c
> > @@ -53,6 +53,12 @@ enum vmd_features {
> >  	 * vendor-specific capability space
> >  	 */
> >  	VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP	= (1 << 2),
> > +
> > +	/*
> > +	 * Device may use MSI/X vector 0 for software triggering and will not
> > +	 * be used for MSI/X remapping
> > +	 */
> > +	VMD_FEAT_OFFSET_FIRST_VECTOR		= (1 << 3),
> >  };
> >  
> >  /*
> > @@ -104,6 +110,7 @@ struct vmd_dev {
> >  	struct irq_domain	*irq_domain;
> >  	struct pci_bus		*bus;
> >  	u8			busn_start;
> > +	u8			first_vec;
> >  };
> >  
> >  static inline struct vmd_dev *vmd_from_bus(struct pci_bus *bus)
> > @@ -199,25 +206,26 @@ static irq_hw_number_t vmd_get_hwirq(struct msi_domain_info *info,
> >   */
> >  static struct vmd_irq_list *vmd_next_irq(struct vmd_dev *vmd, struct msi_desc *desc)
> >  {
> > -	int i, best = 1;
> >  	unsigned long flags;
> > +	int i, best;
> >  
> >  	if (vmd->msix_count == 1)
> 
> This condition needs account for the vector offset, right?
> 
>   	if (vmd->msix_count == 1 + vmd->first_vec))

Looks like it, yes

Thank you

> 
> > -		return &vmd->irqs[0];
> > +		return &vmd->irqs[vmd->first_vec];