Re: [Qemu-devel] [RFC PATCH 07/10] spapr_pci: Allow PCI host bridge DMA window to be configured

[David Gibson]

On Wed, Sep 23, 2015 at 08:55:01PM +0200, Laurent Vivier wrote:
> 
> 
> On 17/09/2015 15:09, David Gibson wrote:
> > At present the PCI host bridge (PHB) for the pseries machine type has a
> > fixed DMA window from 0..1GB (in PCI address space) which is mapped to real
> > memory via the PAPR paravirtualized IOMMU.
> > 
> > For better support of VFIO devices, we're going to want to allow for
> > different configurations of the DMA window.
> > 
> > Eventually we'll want to allow the guest itself to reconfigure the window
> > via the PAPR dynamic DMA window interface, but as a preliminary this patch
> > allows the user to reconfigure the window with new properties on the PHB
> > device.
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >  hw/ppc/spapr_pci.c          | 7 +++++--
> >  include/hw/pci-host/spapr.h | 3 +--
> >  2 files changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index b088491..622c4ac 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -1394,7 +1394,7 @@ static void spapr_phb_finish_realize(sPAPRPHBState 
> > *sphb, Error **errp)
> >      sPAPRTCETable *tcet;
> >      uint32_t nb_table;
> >  
> > -    nb_table = SPAPR_PCI_DMA32_SIZE >> SPAPR_TCE_PAGE_SHIFT;
> > +    nb_table = sphb->dma_win_size >> SPAPR_TCE_PAGE_SHIFT;
> >      tcet = spapr_tce_new_table(DEVICE(sphb), sphb->dma_liobn,
> >                                 0, SPAPR_TCE_PAGE_SHIFT, nb_table, false);
> >      if (!tcet) {
> > @@ -1404,7 +1404,7 @@ static void spapr_phb_finish_realize(sPAPRPHBState 
> > *sphb, Error **errp)
> >      }
> >  
> >      /* Register default 32bit DMA window */
> > -    memory_region_add_subregion(&sphb->iommu_root, 0,
> > +    memory_region_add_subregion(&sphb->iommu_root, sphb->dma_win_addr,
> >                                  spapr_tce_get_iommu(tcet));
> >  }
> >  
> > @@ -1437,6 +1437,9 @@ static Property spapr_phb_properties[] = {
> >                         SPAPR_PCI_IO_WIN_SIZE),
> >      DEFINE_PROP_BOOL("dynamic-reconfiguration", sPAPRPHBState, dr_enabled,
> >                       true),
> > +    /* Default DMA window is 0..1GB */
> > +    DEFINE_PROP_UINT64("dma_win_addr", sPAPRPHBState, dma_win_addr, 0),
> > +    DEFINE_PROP_UINT64("dma_win_size", sPAPRPHBState, dma_win_size, 
> > 0x40000000),
> >      DEFINE_PROP_END_OF_LIST(),
> >  };
> 
> Add them too to the vmstate_spapr_pci ?

No.  At least, not just now.

This is the sort of configuration information that typically isn't
migrated, instead requiring the far end to be set up matching.  Which
is a problem, but not one within the scope of this patch series.  In
any case just transferring the values wouldn't be enough - we'd need
post_load handlers to actually rewire the TCE table accordingly.

We will need to do this once we add dynamic DMA window support, but
again, not in scope just now.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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