Re: [Qemu-devel] [Qemu-ppc] [PATCH qemu v13 04/16] spapr_iommu: Introduce "enabled" state for TCE table

[David Gibson]

On Tue, Mar 01, 2016 at 08:10:29PM +1100, Alexey Kardashevskiy wrote:
> Currently TCE tables are created once at start and their sizes never
> change. We are going to change that by introducing a Dynamic DMA windows
> support where DMA configuration may change during the guest execution.
> 
> This changes spapr_tce_new_table() to create an empty zero-size IOMMU
> memory region (IOMMU MR). Only LIOBN is assigned by the time of creation.
> It still will be called once at the owner object (VIO or PHB) creation.
> 
> This introduces an "enabled" state for TCE table objects with two
> helper functions - spapr_tce_table_enable()/spapr_tce_table_disable().
> - spapr_tce_table_enable() receives TCE table parameters, allocates
> a guest view of the TCE table (in the user space or KVM) and
> sets the correct size on the IOMMU MR.
> - spapr_tce_table_disable() disposes the table and resets the IOMMU MR
> size.
> 
> This changes the PHB reset handler to do the default DMA initialization
> instead of spapr_phb_realize(). This does not make differenct now but
> later with more than just one DMA window, we will have to remove them all
> and create the default one on a system reset.
> 
> No visible change in behaviour is expected except the actual table
> will be reallocated every reset. We might optimize this later.
> 
> The other way to implement this would be dynamically create/remove
> the TCE table QOM objects but this would make migration impossible
> as the migration code expects all QOM objects to exist at the receiver
> so we have to have TCE table objects created when migration begins.
> 
> spapr_tce_table_do_enable() is separated from from spapr_tce_table_enable()
> as later it will be called at the sPAPRTCETable post-migration stage when
> it already has all the properties set after the migration.
> 
> Signed-off-by: Alexey Kardashevskiy <address@hidden>

Reviewed-by: David Gibson <address@hidden>

Although there's one nit that could be improved:


> ---
>  hw/ppc/spapr_iommu.c   | 80 
> +++++++++++++++++++++++++++++++++++---------------
>  hw/ppc/spapr_pci.c     | 21 +++++++++----
>  hw/ppc/spapr_vio.c     |  9 +++---
>  include/hw/ppc/spapr.h | 10 +++----
>  4 files changed, 80 insertions(+), 40 deletions(-)
> 
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index 8132f64..e66e128 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -174,15 +174,8 @@ static int spapr_tce_table_realize(DeviceState *dev)
>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(dev);
>  
>      tcet->fd = -1;
> -    tcet->table = spapr_tce_alloc_table(tcet->liobn,
> -                                        tcet->page_shift,
> -                                        tcet->nb_table,
> -                                        &tcet->fd,
> -                                        tcet->need_vfio);
> -
>      memory_region_init_iommu(&tcet->iommu, OBJECT(dev), &spapr_iommu_ops,
> -                             "iommu-spapr",
> -                             (uint64_t)tcet->nb_table << tcet->page_shift);
> +                             "iommu-spapr", 0);
>  
>      QLIST_INSERT_HEAD(&spapr_tce_tables, tcet, list);
>  
> @@ -224,14 +217,10 @@ void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool 
> need_vfio)
>      tcet->table = newtable;
>  }
>  
> -sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn,
> -                                   uint64_t bus_offset,
> -                                   uint32_t page_shift,
> -                                   uint32_t nb_table,
> -                                   bool need_vfio)
> +sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn)
>  {
>      sPAPRTCETable *tcet;
> -    char tmp[64];
> +    char tmp[32];
>  
>      if (spapr_tce_find_by_liobn(liobn)) {
>          fprintf(stderr, "Attempted to create TCE table with duplicate"
> @@ -239,16 +228,8 @@ sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, 
> uint32_t liobn,
>          return NULL;
>      }
>  
> -    if (!nb_table) {
> -        return NULL;
> -    }
> -
>      tcet = SPAPR_TCE_TABLE(object_new(TYPE_SPAPR_TCE_TABLE));
>      tcet->liobn = liobn;
> -    tcet->bus_offset = bus_offset;
> -    tcet->page_shift = page_shift;
> -    tcet->nb_table = nb_table;
> -    tcet->need_vfio = need_vfio;
>  
>      snprintf(tmp, sizeof(tmp), "tce-table-%x", liobn);
>      object_property_add_child(OBJECT(owner), tmp, OBJECT(tcet), NULL);
> @@ -258,14 +239,65 @@ sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, 
> uint32_t liobn,
>      return tcet;
>  }
>  
> +static void spapr_tce_table_do_enable(sPAPRTCETable *tcet)
> +{
> +    if (!tcet->nb_table) {
> +        return;
> +    }
> +
> +    tcet->table = spapr_tce_alloc_table(tcet->liobn,
> +                                        tcet->page_shift,
> +                                        tcet->nb_table,
> +                                        &tcet->fd,
> +                                        tcet->need_vfio);
> +
> +    memory_region_set_size(&tcet->iommu,
> +                           (uint64_t)tcet->nb_table << tcet->page_shift);
> +
> +    tcet->enabled = true;
> +}
> +
> +void spapr_tce_table_enable(sPAPRTCETable *tcet,
> +                            uint32_t page_shift, uint64_t bus_offset,
> +                            uint32_t nb_table, bool need_vfio)
> +{
> +    if (tcet->enabled) {
> +        return;

If the given parameters are different from the current ones, treating
this as a no-op is rather misleading.  I gather that to resize the
window you're expected to disable, then re-enable.  In which case I
think it would be safer to actually throw some kind of error on a
double enable.


> +    }
> +
> +    tcet->bus_offset = bus_offset;
> +    tcet->page_shift = page_shift;
> +    tcet->nb_table = nb_table;
> +    tcet->need_vfio = need_vfio;
> +
> +    spapr_tce_table_do_enable(tcet);
> +}
> +
> +static void spapr_tce_table_disable(sPAPRTCETable *tcet)
> +{
> +    if (!tcet->enabled) {
> +        return;
> +    }
> +
> +    memory_region_set_size(&tcet->iommu, 0);
> +
> +    spapr_tce_free_table(tcet->table, tcet->fd, tcet->nb_table);
> +    tcet->fd = -1;
> +    tcet->table = NULL;
> +    tcet->enabled = false;
> +    tcet->bus_offset = 0;
> +    tcet->page_shift = 0;
> +    tcet->nb_table = 0;
> +    tcet->need_vfio = false;
> +}
> +
>  static void spapr_tce_table_unrealize(DeviceState *dev, Error **errp)
>  {
>      sPAPRTCETable *tcet = SPAPR_TCE_TABLE(dev);
>  
>      QLIST_REMOVE(tcet, list);
>  
> -    spapr_tce_free_table(tcet->table, tcet->fd, tcet->nb_table);
> -    tcet->fd = -1;
> +    spapr_tce_table_disable(tcet);
>  }
>  
>  MemoryRegion *spapr_tce_get_iommu(sPAPRTCETable *tcet)
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 248f20a..c34a906 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -815,12 +815,13 @@ static int spapr_phb_dma_window_enable(sPAPRPHBState 
> *sphb,
>          return -1;
>      }
>  
> -    tcet = spapr_tce_new_table(DEVICE(sphb), liobn, window_addr,
> -                               page_shift, nb_table, false);
> +    tcet = spapr_tce_find_by_liobn(liobn);
>      if (!tcet) {
>          return -1;
>      }
>  
> +    spapr_tce_table_enable(tcet, page_shift, window_addr, nb_table, false);
> +
>      memory_region_add_subregion(&sphb->iommu_root, tcet->bus_offset,
>                                  spapr_tce_get_iommu(tcet));
>      return 0;
> @@ -1251,6 +1252,7 @@ static void spapr_phb_realize(DeviceState *dev, Error 
> **errp)
>      int i;
>      PCIBus *bus;
>      uint64_t msi_window_size = 4096;
> +    sPAPRTCETable *tcet;
>  
>      if (sphb->index != (uint32_t)-1) {
>          hwaddr windows_base;
> @@ -1402,11 +1404,18 @@ static void spapr_phb_realize(DeviceState *dev, Error 
> **errp)
>          }
>      }
>  
> +    /* DMA setup */
> +    tcet = spapr_tce_new_table(DEVICE(sphb), sphb->dma_liobn);
> +    if (!tcet) {
> +        error_report("No default TCE table for %s", sphb->dtbusname);
> +        return;
> +    }
> +
>      /* Register default 32bit DMA window */
> -    if (spapr_phb_dma_window_enable(sphb, sphb->dma_liobn, 
> SPAPR_TCE_PAGE_SHIFT,
> -                                    sphb->dma_win_addr, sphb->dma_win_size)) 
> {
> -        error_setg(errp, "Unable to create TCE table for %s", 
> sphb->dtbusname);
> -    }
> +    spapr_phb_dma_window_enable(sphb, sphb->dma_liobn,
> +                                SPAPR_TCE_PAGE_SHIFT,
> +                                sphb->dma_win_addr,
> +                                sphb->dma_win_size);
>  
>      sphb->msi = g_hash_table_new_full(g_int_hash, g_int_equal, g_free, 
> g_free);
>  }
> diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
> index 0f61a55..a745884 100644
> --- a/hw/ppc/spapr_vio.c
> +++ b/hw/ppc/spapr_vio.c
> @@ -481,11 +481,10 @@ static void spapr_vio_busdev_realize(DeviceState *qdev, 
> Error **errp)
>          memory_region_add_subregion_overlap(&dev->mrroot, 0, &dev->mrbypass, 
> 1);
>          address_space_init(&dev->as, &dev->mrroot, qdev->id);
>  
> -        dev->tcet = spapr_tce_new_table(qdev, liobn,
> -                                        0,
> -                                        SPAPR_TCE_PAGE_SHIFT,
> -                                        pc->rtce_window_size >>
> -                                        SPAPR_TCE_PAGE_SHIFT, false);
> +        dev->tcet = spapr_tce_new_table(qdev, liobn);
> +        spapr_tce_table_enable(dev->tcet, SPAPR_TCE_PAGE_SHIFT, 0,
> +                               pc->rtce_window_size >> SPAPR_TCE_PAGE_SHIFT,
> +                               false);
>          dev->tcet->vdev = dev;
>          memory_region_add_subregion_overlap(&dev->mrroot, 0,
>                                              spapr_tce_get_iommu(dev->tcet), 
> 2);
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 098d85d..3e6bb84 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -539,6 +539,7 @@ typedef struct sPAPRTCETable sPAPRTCETable;
>  
>  struct sPAPRTCETable {
>      DeviceState parent;
> +    bool enabled;
>      uint32_t liobn;
>      uint32_t nb_table;
>      uint64_t bus_offset;
> @@ -566,11 +567,10 @@ void spapr_events_fdt_skel(void *fdt, uint32_t 
> epow_irq);
>  int spapr_h_cas_compose_response(sPAPRMachineState *sm,
>                                   target_ulong addr, target_ulong size,
>                                   bool cpu_update, bool memory_update);
> -sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn,
> -                                   uint64_t bus_offset,
> -                                   uint32_t page_shift,
> -                                   uint32_t nb_table,
> -                                   bool need_vfio);
> +sPAPRTCETable *spapr_tce_new_table(DeviceState *owner, uint32_t liobn);
> +void spapr_tce_table_enable(sPAPRTCETable *tcet,
> +                            uint32_t page_shift, uint64_t bus_offset,
> +                            uint32_t nb_table, bool vfio_accel);
>  void spapr_tce_set_need_vfio(sPAPRTCETable *tcet, bool need_vfio);
>  
>  MemoryRegion *spapr_tce_get_iommu(sPAPRTCETable *tcet);

-- 
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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