Re: [Qemu-devel] [RFC 1/4] spapr_pci: Delegate placement of PCI host bridges to machine type

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/10/16 14:03, David Gibson wrote:
> The 'spapr-pci-host-bridge' represents the virtual PCI host bridge (PHB)
> for a PAPR guest.  Unlike on x86, it's routine on Power (both bare metal
> and PAPR guests) to have numerous independent PHBs, each controlling a
> separate PCI domain.
> 
> There are two ways of configuring the spapr-pci-host-bridge device: first
> it can be done fully manually, specifying the locations and sizes of all
> the IO windows.  This gives the most control, but is very awkward with 6
> mandatory parameters.  Alternatively just an "index" can be specified
> which essentially selects from an array of predefined PHB locations.
> The PHB at index 0 is automatically created as the default PHB.
> 
> The current set of default locations causes some problems for guests with
> large RAM (> 1 TiB) or PCI devices with very large BARs (e.g. big nVidia
> GPGPU cards via VFIO).  Obviously, for migration we can only change the
> locations on a new machine type, however.
> 
> This is awkward, because the placement is currently decided within the
> spapr-pci-host-bridge code, so it breaks abstraction to look inside the
> machine type version.
> 
> So, this patch delegates the "default mode" PHB placement from the
> spapr-pci-host-bridge device back to the machine type via a public method
> in sPAPRMachineClass.  It's still a bit ugly, but it's about the best we
> can do.
> 
> For now, this just changes where the calculation is done.  It doesn't
> change the actual location of the host bridges, or any other behaviour.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c              | 34 ++++++++++++++++++++++++++++++++++
>  hw/ppc/spapr_pci.c          | 22 ++++++++--------------
>  include/hw/pci-host/spapr.h | 11 +----------
>  include/hw/ppc/spapr.h      |  4 ++++
>  4 files changed, 47 insertions(+), 24 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 03e3803..f6e9c2a 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2370,6 +2370,39 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
>      return head;
>  }
>  
> +static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
> +                                uint64_t *buid, hwaddr *pio, hwaddr *pio_size,
> +                                hwaddr *mmio, hwaddr *mmio_size,
> +                                unsigned n_dma, uint32_t *liobns, Error **errp)
> +{
> +    const uint64_t base_buid = 0x800000020000000ULL;
> +    const hwaddr phb0_base = 0x10000000000ULL; /* 1 TiB */
> +    const hwaddr phb_spacing = 0x1000000000ULL; /* 64 GiB */
> +    const hwaddr mmio_offset = 0xa0000000; /* 2 GiB + 512 MiB */
> +    const hwaddr pio_offset = 0x80000000; /* 2 GiB */
> +    const uint32_t max_index = 255;
> +
> +    hwaddr phb_base;
> +    int i;
> +
> +    if (index > max_index) {
> +        error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
> +                   max_index);
> +        return;
> +    }
> +
> +    *buid = base_buid + index;
> +    for (i = 0; i < n_dma; ++i) {
> +        liobns[i] = SPAPR_PCI_LIOBN(index, i);
> +    }
> +
> +    phb_base = phb0_base + index * phb_spacing;
> +    *pio = phb_base + pio_offset;
> +    *pio_size = SPAPR_PCI_IO_WIN_SIZE;
> +    *mmio = phb_base + mmio_offset;
> +    *mmio_size = SPAPR_PCI_MMIO_WIN_SIZE;
> +}
> +
>  static void spapr_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> @@ -2406,6 +2439,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
>      mc->query_hotpluggable_cpus = spapr_query_hotpluggable_cpus;
>      fwc->get_dev_path = spapr_get_fw_dev_path;
>      nc->nmi_monitor_handler = spapr_nmi;
> +    smc->phb_placement = spapr_phb_placement;
>  }
>  
>  static const TypeInfo spapr_machine_info = {
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 4f00865..c0fc964 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -1311,7 +1311,8 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
>          sphb->ddw_enabled ? SPAPR_PCI_DMA_MAX_WINDOWS : 1;
>  
>      if (sphb->index != (uint32_t)-1) {
> -        hwaddr windows_base;
> +        sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
> +        Error *local_err = NULL;
>  
>          if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn[0] != (uint32_t)-1)
>              || (sphb->dma_liobn[1] != (uint32_t)-1 && windows_supported == 2)
> @@ -1322,21 +1323,14 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
>              return;
>          }
>  
> -        if (sphb->index > SPAPR_PCI_MAX_INDEX) {
> -            error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
> -                       SPAPR_PCI_MAX_INDEX);
> +        smc->phb_placement(spapr, sphb->index,
> +                           &sphb->buid, &sphb->io_win_addr, &sphb->io_win_size,
> +                           &sphb->mem_win_addr, &sphb->mem_win_size,
> +                           windows_supported, sphb->dma_liobn, &local_err);
> +        if (local_err) {
> +            error_propagate(errp, local_err);
>              return;
>          }
> -
> -        sphb->buid = SPAPR_PCI_BASE_BUID + sphb->index;
> -        for (i = 0; i < windows_supported; ++i) {
> -            sphb->dma_liobn[i] = SPAPR_PCI_LIOBN(sphb->index, i);
> -        }
> -
> -        windows_base = SPAPR_PCI_WINDOW_BASE
> -            + sphb->index * SPAPR_PCI_WINDOW_SPACING;
> -        sphb->mem_win_addr = windows_base + SPAPR_PCI_MMIO_WIN_OFF;
> -        sphb->io_win_addr = windows_base + SPAPR_PCI_IO_WIN_OFF;
>      }
>  
>      if (sphb->buid == (uint64_t)-1) {
> diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
> index 30dbd46..8c9ebfd 100644
> --- a/include/hw/pci-host/spapr.h
> +++ b/include/hw/pci-host/spapr.h
> @@ -79,18 +79,9 @@ struct sPAPRPHBState {
>      uint32_t numa_node;
>  };
>  
> -#define SPAPR_PCI_MAX_INDEX          255
> -
> -#define SPAPR_PCI_BASE_BUID          0x800000020000000ULL
> -
>  #define SPAPR_PCI_MEM_WIN_BUS_OFFSET 0x80000000ULL
>  
> -#define SPAPR_PCI_WINDOW_BASE        0x10000000000ULL
> -#define SPAPR_PCI_WINDOW_SPACING     0x1000000000ULL
> -#define SPAPR_PCI_MMIO_WIN_OFF       0xA0000000
> -#define SPAPR_PCI_MMIO_WIN_SIZE      (SPAPR_PCI_WINDOW_SPACING - \
> -                                     SPAPR_PCI_MEM_WIN_BUS_OFFSET)
> -#define SPAPR_PCI_IO_WIN_OFF         0x80000000
> +#define SPAPR_PCI_MMIO_WIN_SIZE      0xf80000000
>  #define SPAPR_PCI_IO_WIN_SIZE        0x10000
>  
>  #define SPAPR_PCI_MSI_WINDOW         0x40000000000ULL
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 39dadaa..9e1c5a5 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -40,6 +40,10 @@ struct sPAPRMachineClass {
>      bool dr_lmb_enabled;       /* enable dynamic-reconfig/hotplug of LMBs */
>      bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
>      const char *tcg_default_cpu; /* which (TCG) CPU to simulate by default */
> +    void (*phb_placement)(sPAPRMachineState *spapr, uint32_t index,
> +                          uint64_t *buid, hwaddr *pio, hwaddr *pio_size,
> +                          hwaddr *mmio, hwaddr *mmio_size,
> +                          unsigned n_dma, uint32_t *liobns, Error **errp);


I still like idea of getting rid of index better. In order to reduce the
command line length, you could not enable IO and MMIO32 by default, the
default size for MMIO64 could be set to 1TB or something like this, BUID
could be just a raw MMIO64 address value.

So essentially you would only have to specify MMIO64 and 2xLIOBN in the
command line which does not seem that much of overkill assuming that a
second (third,...) PHB is almost never used and even if it is, it will be
used for SRIOV VF (which can do 64bit) or virtio (the same).

With index and phb_placement(), QEMU will still auto-generate these IO/MMIO
addresses from the command line parameters which did hit us with migration
before as the QEMU command line on the source side and the destination side
is not exactly the same, and this might hit again...



>  };
>  
>  /**
> 


-- 
Alexey