Re: [Qemu-devel] [PATCH qemu v15 15/17] spapr_pci: Get rid of dma_loibn

[Alexey Kardashevskiy]

On 04/07/2016 10:50 AM, David Gibson wrote:
> s/dma_loibn/dma_liobn/ in subject line.
>
> On Mon, Apr 04, 2016 at 07:33:44PM +1000, Alexey Kardashevskiy wrote:
> > We are going to have 2 DMA windows which LIOBNs are calculated from
> > the PHB index and the window number using the SPAPR_PCI_LIOBN macro
> > so there is no actual use for dma_liobn.
> >
> > This replaces dma_liobn with SPAPR_PCI_LIOBN. This marks it as unused
> > in the migration stream. This renames dma_liobn to _dma_liobn as we have
> > to keep the property for the CLI compatibility and we need a storage
> > for it, although it has never really been used.
> >
> > Signed-off-by: Alexey Kardashevskiy <address@hidden>
>
> This doesn't quite make sense.  We can't really do that without
> entirely removing support for PHBs without an 'index' value.
> Basically the idea of the PHB config parameters what that you either
> specified just "index" or you specified *all* the relevant addresses.
> Removing option 2 might be a reasonable idea, but it shouldn't just be
> done as a side effect of this other change.  With this patch the
> "specify everything" approach still has code, but can't work, because
> such a device will never get a reasonable liobn (or worse, it might
> get a duplicate liobn, because the index isn't verified in this mode).
>
> Then again.. the "index" approach has also bitten us with the problem
> of the not-quite-big-enough MMIO space per-PHB,

Any new ideas on that front? I also keep in mind that we rather want to 
assign interrupt numbers pool to a PHB based on its index rather than 
allocate them from the global machine interrupt number space so this is one 
more vote for keeping the index.


> so I'm not entirely
> sure that making it the only choice is the right way to go either.

I can imagine the user wanting to change MMIO addresses (so they should 
remain properties) but changing LIOBN from the command line does not seem 
useful at all.


> The short term approach to handle DDW might be to instead add a
> dma64_liobn property.

So everywhere where I want to have a loop through all TCE tables and use 
SPAPR_PCI_LIOBN(index, i), I cannot really do that if I have 2 separate 
properties. Not extremely convenient.



> > ---
> > Changes:
> > v15:
> > * new to the series
> > ---
> >   hw/ppc/spapr_pci.c          | 17 ++++++-----------
> >   include/hw/pci-host/spapr.h |  2 +-
> >   2 files changed, 7 insertions(+), 12 deletions(-)
> >
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index f864fde..d4bdb27 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -1306,7 +1306,7 @@ static void spapr_phb_realize(DeviceState *dev, Error 
> > **errp)
> >       if (sphb->index != (uint32_t)-1) {
> >           hwaddr windows_base;
> >
> > -        if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn != (uint32_t)-1)
> > +        if ((sphb->buid != (uint64_t)-1)
> >               || (sphb->mem_win_addr != (hwaddr)-1)
> >               || (sphb->io_win_addr != (hwaddr)-1)) {
> >               error_setg(errp, "Either \"index\" or other parameters must"
> > @@ -1321,7 +1321,6 @@ static void spapr_phb_realize(DeviceState *dev, Error 
> > **errp)
> >           }
> >
> >           sphb->buid = SPAPR_PCI_BASE_BUID + sphb->index;
> > -        sphb->dma_liobn = SPAPR_PCI_LIOBN(sphb->index, 0);
> >
> >           windows_base = SPAPR_PCI_WINDOW_BASE
> >               + sphb->index * SPAPR_PCI_WINDOW_SPACING;
> > @@ -1334,11 +1333,6 @@ static void spapr_phb_realize(DeviceState *dev, Error 
> > **errp)
> >           return;
> >       }
> >
> > -    if (sphb->dma_liobn == (uint32_t)-1) {
> > -        error_setg(errp, "LIOBN not specified for PHB");
> > -        return;
> > -    }
> > -
> >       if (sphb->mem_win_addr == (hwaddr)-1) {
> >           error_setg(errp, "Memory window address not specified for PHB");
> >           return;
> > @@ -1453,7 +1447,7 @@ static void spapr_phb_realize(DeviceState *dev, Error 
> > **errp)
> >           }
> >       }
> >
> > -    tcet = spapr_tce_new_table(DEVICE(sphb), sphb->dma_liobn);
> > +    tcet = spapr_tce_new_table(DEVICE(sphb), SPAPR_PCI_LIOBN(sphb->index, 0));
> >       if (!tcet) {
> >           error_setg(errp, "Unable to create TCE table for %s",
> >                      sphb->dtbusname);
> > @@ -1479,7 +1473,8 @@ static int spapr_phb_children_reset(Object *child, void 
> > *opaque)
> >
> >   void spapr_phb_dma_reset(sPAPRPHBState *sphb)
> >   {
> > -    sPAPRTCETable *tcet = spapr_tce_find_by_liobn(sphb->dma_liobn);
> > +    uint32_t liobn = SPAPR_PCI_LIOBN(sphb->index, 0);
> > +    sPAPRTCETable *tcet = spapr_tce_find_by_liobn(liobn);
> >
> >       if (tcet && tcet->enabled) {
> >           spapr_tce_table_disable(tcet);
> > @@ -1507,7 +1502,7 @@ static void spapr_phb_reset(DeviceState *qdev)
> >   static Property spapr_phb_properties[] = {
> >       DEFINE_PROP_UINT32("index", sPAPRPHBState, index, -1),
> >       DEFINE_PROP_UINT64("buid", sPAPRPHBState, buid, -1),
> > -    DEFINE_PROP_UINT32("liobn", sPAPRPHBState, dma_liobn, -1),
> > +    DEFINE_PROP_UINT32("liobn", sPAPRPHBState, _dma_liobn, -1),
> >       DEFINE_PROP_UINT64("mem_win_addr", sPAPRPHBState, mem_win_addr, -1),
> >       DEFINE_PROP_UINT64("mem_win_size", sPAPRPHBState, mem_win_size,
> >                          SPAPR_PCI_MMIO_WIN_SIZE),
> > @@ -1595,7 +1590,7 @@ static const VMStateDescription vmstate_spapr_pci = {
> >       .post_load = spapr_pci_post_load,
> >       .fields = (VMStateField[]) {
> >           VMSTATE_UINT64_EQUAL(buid, sPAPRPHBState),
> > -        VMSTATE_UINT32_EQUAL(dma_liobn, sPAPRPHBState),
> > +        VMSTATE_UNUSED(4), /* former dma_liobn */
> >           VMSTATE_UINT64_EQUAL(mem_win_addr, sPAPRPHBState),
> >           VMSTATE_UINT64_EQUAL(mem_win_size, sPAPRPHBState),
> >           VMSTATE_UINT64_EQUAL(io_win_addr, sPAPRPHBState),
> > diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
> > index 7848366..3fca1c3 100644
> > --- a/include/hw/pci-host/spapr.h
> > +++ b/include/hw/pci-host/spapr.h
> > @@ -56,7 +56,7 @@ struct sPAPRPHBState {
> >       hwaddr mem_win_addr, mem_win_size, io_win_addr, io_win_size;
> >       MemoryRegion memwindow, iowindow, msiwindow;
> >
> > -    uint32_t dma_liobn;
> > +    uint32_t _dma_liobn;
> >       hwaddr dma_win_addr, dma_win_size;
> >       AddressSpace iommu_as;
> >       MemoryRegion iommu_root;


--
Alexey