Re: [Qemu-devel] [PATCH v6 5/6] spapr_pci: populate ibm,loc-code

[Thomas Huth <thuth@redhat.com>]

On Wed,  3 Jun 2015 16:55:56 +0530
Nikunj A Dadhania <nikunj@linux.vnet.ibm.com> wrote:

> Each hardware instance has a platform unique location code.  The OF
> device tree that describes a part of a hardware entity must include
> the “ibm,loc-code” property with a value that represents the location
> code for that hardware entity.
> 
> Populate ibm,loc-code.
> 
> 1) PCI passthru devices need to identify with its own ibm,loc-code
>    available on the host. In failure cases use:
>    vfio_<name>:<phb-index>:<bus>:<slot>.<fn>
> 
> 2) Emulated devices encode as following:
>    qemu_<name>:<phb-index>:<bus>:<slot>.<fn>
> 
> Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr_pci.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 68 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 4226468..986bb21 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -746,6 +746,60 @@ static AddressSpace *spapr_pci_dma_iommu(PCIBus *bus, void *opaque, int devfn)
>      return &phb->iommu_as;
>  }
>  
> +static char *spapr_phb_vfio_get_loc_code(sPAPRPHBState *sphb,  PCIDevice *pdev)
> +{
> +    char *path = NULL, *buf = NULL, *host = NULL;
> +
> +    /* Get the PCI VFIO host id */
> +    host = object_property_get_str(OBJECT(pdev), "host", NULL);
> +    if (!host) {
> +        goto err_out;
> +    }
> +
> +    /* Construct the path of the file that will give us the DT location */
> +    path = g_strdup_printf("/sys/bus/pci/devices/%s/devspec", host);
> +    g_free(host);
> +    if (!path || !g_file_get_contents(path, &buf, NULL, NULL)) {
> +        goto err_out;
> +    }
> +    g_free(path);
> +
> +    /* Construct and read from host device tree the loc-code */
> +    path = g_strdup_printf("/proc/device-tree%s/ibm,loc-code", buf);
> +    g_free(buf);
> +    if (!path || !g_file_get_contents(path, &buf, NULL, NULL)) {
> +        goto err_out;
> +    }
> +    return buf;

I'd maybe change the above 4 lines into:

    if (path && g_file_get_contents(path, &buf, NULL, NULL)) {
        return buf;
    }

so that you can get rid of one goto here.

> +err_out:
> +    g_free(path);
> +    return NULL;
> +}
> +
> +static char *spapr_phb_get_loc_code(sPAPRPHBState *sphb, PCIDevice *pdev)
> +{
> +    char *buf;
> +    const char *devtype = "qemu";
> +    uint32_t busnr = pci_bus_num(PCI_BUS(qdev_get_parent_bus(DEVICE(pdev))));
> +
> +    if (object_dynamic_cast(OBJECT(pdev), "vfio-pci")) {
> +        buf = spapr_phb_vfio_get_loc_code(sphb, pdev);
> +        if (buf) {
> +            return buf;
> +        }
> +        devtype = "vfio";
> +    }
> +    /*
> +     * For emulated devices and VFIO-failure case, make up
> +     * the loc-code.
> +     */
> +    buf = g_strdup_printf("%s_%s:%04x:%02x:%02x.%x",
> +                          devtype, pdev->name, sphb->index, busnr,
> +                          PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));
> +    return buf;
> +}
> +
>  /* Macros to operate with address in OF binding to PCI */
>  #define b_x(x, p, l)    (((x) & ((1<<(l))-1)) << (p))
>  #define b_n(x)          b_x((x), 31, 1) /* 0 if relocatable */
> @@ -884,11 +938,12 @@ static void populate_resource_props(PCIDevice *d, ResourceProps *rp)
>  
>  static int spapr_populate_pci_child_dt(PCIDevice *dev, void *fdt, int offset,
>                                         int phb_index, int drc_index,
> -                                       const char *drc_name)
> +                                       sPAPRPHBState *sphb)
>  {
>      ResourceProps rp;
>      bool is_bridge = false;
>      int pci_status;
> +    char *buf = NULL;

Is the "= NULL" required here? If not, please remove, newer version
of gcc tend to complain otherwise.

>      if (pci_default_read_config(dev, PCI_HEADER_TYPE, 1) ==
>          PCI_HEADER_TYPE_BRIDGE) {
> @@ -949,10 +1004,15 @@ static int spapr_populate_pci_child_dt(PCIDevice *dev, void *fdt, int offset,
>       * processed by OF beforehand
>       */
>      _FDT(fdt_setprop_string(fdt, offset, "name", "pci"));
> -    if (drc_name) {
> -        _FDT(fdt_setprop(fdt, offset, "ibm,loc-code", drc_name,
> -                         strlen(drc_name)));
> +    buf = spapr_phb_get_loc_code(sphb, dev);
> +    if (!buf) {
> +        error_report("Failed setting the ibm,loc-code");
> +        return -1;
>      }
> +
> +    _FDT(fdt_setprop_string(fdt, offset, "ibm,loc-code", buf));

I wonder whether this will cause some Coverity warnings later ...
the _FDT macro can return immediately (ugh, return in a macro ... IMHO
a bad idea...). buf is not freed in that case, and that might trigger a
warning...

> +    g_free(buf);
> +
>      if (drc_index) {
>          _FDT(fdt_setprop_cell(fdt, offset, "ibm,my-drc-index", drc_index));
>      }
[...]

 Thomas