Re: [Qemu-devel] [PATCH v3 6/6] spapr_pci: populate ibm,loc-code

[Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>]

Thomas Huth <thuth@redhat.com> writes:

> On Tue,  5 May 2015 14:23:56 +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.
>> 2) Emulated devices encode as following:
>>    qemu_<name>:<phb-index>:<slot>.<fn>
>> 
>> Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
>> ---
>>  hw/ppc/spapr_pci.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++-------
>>  1 file changed, 75 insertions(+), 11 deletions(-)
>> 
>> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
>> index cbd5661..eacf0bd 100644
>> --- a/hw/ppc/spapr_pci.c
>> +++ b/hw/ppc/spapr_pci.c
>> @@ -744,6 +744,70 @@ static AddressSpace *spapr_pci_dma_iommu(PCIBus *bus, void *opaque, int devfn)
>>      return &phb->iommu_as;
>>  }
>>  
>> +static bool spapr_phb_vfio_get_devspec_value(PCIDevice *pdev, char **value)
>> +{
>> +    char *host;
>> +    char path[PATH_MAX];
>> +
>> +    host = object_property_get_str(OBJECT(pdev), "host", NULL);
>> +    if (!host) {
>> +        return false;
>> +    }
>> +
>> +    snprintf(path, sizeof(path), "/sys/bus/pci/devices/%s/devspec", host);
>> +    g_free(host);
>> +
>> +    return g_file_get_contents(path, value, NULL, NULL);
>> +}
>> +
>> +static char *spapr_phb_vfio_get_loc_code(sPAPRPHBState *sphb,  PCIDevice *pdev)
>> +{
>> +    char path[PATH_MAX], *buf = NULL;
>> +
>> +    /* We have a vfio host bridge lets get the path. */
>> +    if (!spapr_phb_vfio_get_devspec_value(pdev, &buf)) {
>> +        return NULL;
>> +    }
>> +
>> +    snprintf(path, sizeof(path), "/proc/device-tree%s/ibm,loc-code", buf);
>> +    g_free(buf);
>> +
>> +    if (g_file_get_contents(path, &buf, NULL, NULL)) {
>> +        return buf;
>> +    } else {
>> +        return NULL;
>> +    }
>
> Minor idea for an optimization: g_file_get_contents() should set buf to
> NULL in case of errors anyway, so you could omit the "if" and
> "return NULLL" and simply always "return buf" here.

Sure

>
>> +}
>> +
>> +static char *spapr_phb_get_loc_code(sPAPRPHBState *sphb,  PCIDevice *pdev)
>> +{
>> +    char *path = g_malloc(PATH_MAX);
>> +
>> +    if (!path) {
>> +        return NULL;
>> +    }
>> +
>> +    /*
>> +     * For non-vfio devices and failures make up the location code out
>
> This comment ("and failures") ...

Oh right, one option is to drop that...

>
>> +     * of the name, slot and function.
>> +     *
>> +     *       qemu_<name>:<phb-index>:<slot>.<fn>
>> +     */
>> +    snprintf(path, PATH_MAX, "qemu_%s:%02d:%02d.%1d", pdev->name,
>> +             sphb->index, PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));
>> +    return path;
>> +}
>> +
>> +
>> +static char *spapr_ibm_get_loc_code(sPAPRPHBState *sphb, PCIDevice *pdev)
>> +{
>> +    if (object_dynamic_cast(OBJECT(pdev), "vfio-pci") != NULL) {
>> +        return spapr_phb_vfio_get_loc_code(sphb, pdev);
>> +    } else {
>> +        return spapr_phb_get_loc_code(sphb, pdev);
>> +    }
>
> ... does not match quite the behavior here, as far as I can see. I
> guess you also wanted to fall back to spapr_phb_get_loc_code() in case 
> spapr_phb_vfio_get_loc_code() did not work as expected (eg. when the
> access to the /sys or /proc filesystem failed)?

... In current case, if getting vfio device loc_code fails, we would not
 add any ibm,loc_code info. I thought that would be the proper
 behaviour. As "qemu_" would indicate it as an emulated device, which is
 not true. Or encode it as follows:

"vfio_<name>:<phb-index>:<slot>.<fn>"

So more checks would be needed here in that case:

if (vfio) {
   buf = vfio_get_loc_code()
   if (!buf) 
      buf = cook_vfio_get_loc_code()
   return buf;
} else { ... }

>
>> +}
>> +
>>  /* 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 */
>> @@ -881,12 +945,12 @@ 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 *phb, int drc_index)
>
> As David already noted, the sPAPRPHBState related hunks likely rather
> belong to an earlier patch already?

Yes, I will take care, this resuled while juggling with the patches :-)

Regards
Nikunj