Re: [RFC for-5.1 1/4] spapr: Refactor locating NVLink2 devices for device tree creation

[Greg Kurz <groug@kaod.org>]

On Thu, 26 Mar 2020 16:40:06 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Currently spapr_phb_nvgpu_populate_pcidev_dt() works a little cryptically.
> It steps through all the NVLink2 GPUs and NPUs and if they match the device
> we're called for, we generate the relevant device tree information.
> 
> Make this a little more obvious by introducing helpers to determine it a

... to determine if a

> given PCI device is an NVLink2 GPU or NPU, returning the NVLink2 slot and
> link number information as well.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---

LGTM

Reviewed-by: Greg Kurz <groug@kaod.org>

>  hw/ppc/spapr_pci_nvlink2.c | 115 +++++++++++++++++++++++++------------
>  1 file changed, 79 insertions(+), 36 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci_nvlink2.c b/hw/ppc/spapr_pci_nvlink2.c
> index 8332d5694e..7d3a685421 100644
> --- a/hw/ppc/spapr_pci_nvlink2.c
> +++ b/hw/ppc/spapr_pci_nvlink2.c
> @@ -390,13 +390,12 @@ void spapr_phb_nvgpu_ram_populate_dt(SpaprPhbState *sphb, void *fdt)
>  
>  }
>  
> -void spapr_phb_nvgpu_populate_pcidev_dt(PCIDevice *dev, void *fdt, int offset,
> -                                        SpaprPhbState *sphb)
> +static bool is_nvgpu(PCIDevice *dev, SpaprPhbState *sphb, int *slot)
>  {
> -    int i, j;
> +    int i;
>  
>      if (!sphb->nvgpus) {
> -        return;
> +        return false;
>      }
>  
>      for (i = 0; i < sphb->nvgpus->num; ++i) {
> @@ -406,47 +405,91 @@ void spapr_phb_nvgpu_populate_pcidev_dt(PCIDevice *dev, void *fdt, int offset,
>          if (!nvslot->gpdev) {
>              continue;
>          }
> +
>          if (dev == nvslot->gpdev) {
> -            uint32_t npus[nvslot->linknum];
> +            if (slot) {
> +                *slot = i;
> +            }
> +            return true;
> +        }
> +    }
>  
> -            for (j = 0; j < nvslot->linknum; ++j) {
> -                PCIDevice *npdev = nvslot->links[j].npdev;
> +    return false;
> +}
>  
> -                npus[j] = cpu_to_be32(PHANDLE_PCIDEV(sphb, npdev));
> -            }
> -            _FDT(fdt_setprop(fdt, offset, "ibm,npu", npus,
> -                             j * sizeof(npus[0])));
> -            _FDT((fdt_setprop_cell(fdt, offset, "phandle",
> -                                   PHANDLE_PCIDEV(sphb, dev))));
> +static bool is_nvnpu(PCIDevice *dev, SpaprPhbState *sphb, int *slot, int *link)
> +{
> +    int i, j;
> +
> +    if (!sphb->nvgpus) {
> +        return false;
> +    }
> +
> +    for (i = 0; i < sphb->nvgpus->num; ++i) {
> +        SpaprPhbPciNvGpuSlot *nvslot = &sphb->nvgpus->slots[i];
> +
> +        /* Skip "slot" without attached GPU */
> +        if (!nvslot->gpdev) {
>              continue;
>          }
>  
>          for (j = 0; j < nvslot->linknum; ++j) {
> -            if (dev != nvslot->links[j].npdev) {
> -                continue;
> +            if (dev == nvslot->links[j].npdev) {
> +                if (slot) {
> +                    *slot = i;
> +                }
> +                if (link) {
> +                    *link = j;
> +                }
> +                return true;
>              }
> +        }
> +    }
>  
> -            _FDT((fdt_setprop_cell(fdt, offset, "phandle",
> -                                   PHANDLE_PCIDEV(sphb, dev))));
> -            _FDT(fdt_setprop_cell(fdt, offset, "ibm,gpu",
> -                                  PHANDLE_PCIDEV(sphb, nvslot->gpdev)));
> -            _FDT((fdt_setprop_cell(fdt, offset, "ibm,nvlink",
> -                                   PHANDLE_NVLINK(sphb, i, j))));
> -            /*
> -             * If we ever want to emulate GPU RAM at the same location as on
> -             * the host - here is the encoding GPA->TGT:
> -             *
> -             * gta  = ((sphb->nv2_gpa >> 42) & 0x1) << 42;
> -             * gta |= ((sphb->nv2_gpa >> 45) & 0x3) << 43;
> -             * gta |= ((sphb->nv2_gpa >> 49) & 0x3) << 45;
> -             * gta |= sphb->nv2_gpa & ((1UL << 43) - 1);
> -             */
> -            _FDT(fdt_setprop_cell(fdt, offset, "memory-region",
> -                                  PHANDLE_GPURAM(sphb, i)));
> -            _FDT(fdt_setprop_u64(fdt, offset, "ibm,device-tgt-addr",
> -                                 nvslot->tgt));
> -            _FDT(fdt_setprop_cell(fdt, offset, "ibm,nvlink-speed",
> -                                  nvslot->links[j].link_speed));
> +    return false;
> +}
> +
> +void spapr_phb_nvgpu_populate_pcidev_dt(PCIDevice *dev, void *fdt, int offset,
> +                                        SpaprPhbState *sphb)
> +{
> +    int slot, link;
> +
> +    if (is_nvgpu(dev, sphb, &slot)) {
> +        SpaprPhbPciNvGpuSlot *nvslot = &sphb->nvgpus->slots[slot];
> +        uint32_t npus[nvslot->linknum];
> +
> +        for (link = 0; link < nvslot->linknum; ++link) {
> +            PCIDevice *npdev = nvslot->links[link].npdev;
> +
> +            npus[link] = cpu_to_be32(PHANDLE_PCIDEV(sphb, npdev));
>          }
> +        _FDT(fdt_setprop(fdt, offset, "ibm,npu", npus,
> +                         link * sizeof(npus[0])));
> +        _FDT((fdt_setprop_cell(fdt, offset, "phandle",
> +                               PHANDLE_PCIDEV(sphb, dev))));
> +    } else if (is_nvnpu(dev, sphb, &slot, &link)) {
> +        SpaprPhbPciNvGpuSlot *nvslot = &sphb->nvgpus->slots[slot];
> +
> +        _FDT((fdt_setprop_cell(fdt, offset, "phandle",
> +                               PHANDLE_PCIDEV(sphb, dev))));
> +        _FDT(fdt_setprop_cell(fdt, offset, "ibm,gpu",
> +                              PHANDLE_PCIDEV(sphb, nvslot->gpdev)));
> +        _FDT((fdt_setprop_cell(fdt, offset, "ibm,nvlink",
> +                               PHANDLE_NVLINK(sphb, slot, link))));
> +        /*
> +         * If we ever want to emulate GPU RAM at the same location as
> +         * on the host - here is the encoding GPA->TGT:
> +         *
> +         * gta  = ((sphb->nv2_gpa >> 42) & 0x1) << 42;
> +         * gta |= ((sphb->nv2_gpa >> 45) & 0x3) << 43;
> +         * gta |= ((sphb->nv2_gpa >> 49) & 0x3) << 45;
> +         * gta |= sphb->nv2_gpa & ((1UL << 43) - 1);
> +         */
> +        _FDT(fdt_setprop_cell(fdt, offset, "memory-region",
> +                              PHANDLE_GPURAM(sphb, slot)));
> +        _FDT(fdt_setprop_u64(fdt, offset, "ibm,device-tgt-addr",
> +                             nvslot->tgt));
> +        _FDT(fdt_setprop_cell(fdt, offset, "ibm,nvlink-speed",
> +                              nvslot->links[link].link_speed));
>      }
>  }