Re: [PULL v2 11/19] pci: acpi: ensure that acpi-index is unique

[Igor Mammedov]

On Tue, 6 Apr 2021 16:07:25 +0100
Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Tue, Apr 06, 2021 at 03:54:24PM +0100, Daniel P. Berrangé wrote:
> > On Mon, Mar 22, 2021 at 07:00:18PM -0400, Michael S. Tsirkin wrote:  
> > > From: Igor Mammedov <imammedo@redhat.com>
> > > 
> > > it helps to avoid device naming conflicts when guest OS is
> > > configured to use acpi-index for naming.
> > > Spec ialso says so:
> > > 
> > > PCI Firmware Specification Revision 3.2
> > > 4.6.7.  _DSM for Naming a PCI or PCI Express Device Under Operating 
> > > Systems
> > > "
> > > Instance number must be unique under \_SB scope. This instance number 
> > > does not have to
> > > be sequential in a given system configuration.
> > > "
> > > 
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > Message-Id: <20210315180102.3008391-4-imammedo@redhat.com>
> > > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > >  hw/acpi/pcihp.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 46 insertions(+)
> > > 
> > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
> > > index ceab287bd3..f4cb3c979d 100644
> > > --- a/hw/acpi/pcihp.c
> > > +++ b/hw/acpi/pcihp.c
> > > @@ -52,6 +52,21 @@ typedef struct AcpiPciHpFind {
> > >      PCIBus *bus;
> > >  } AcpiPciHpFind;
> > >  
> > > +static gint g_cmp_uint32(gconstpointer a, gconstpointer b, gpointer 
> > > user_data)
> > > +{
> > > +    return a - b;
> > > +}
> > > +
> > > +static GSequence *pci_acpi_index_list(void)
> > > +{
> > > +    static GSequence *used_acpi_index_list;
> > > +
> > > +    if (!used_acpi_index_list) {
> > > +        used_acpi_index_list = g_sequence_new(NULL);
> > > +    }
> > > +    return used_acpi_index_list;
> > > +}
> > > +
> > >  static int acpi_pcihp_get_bsel(PCIBus *bus)
> > >  {
> > >      Error *local_err = NULL;
> > > @@ -277,6 +292,23 @@ void acpi_pcihp_device_pre_plug_cb(HotplugHandler 
> > > *hotplug_dev,
> > >                     ONBOARD_INDEX_MAX);
> > >          return;
> > >      }
> > > +
> > > +    /*
> > > +     * make sure that acpi-index is unique across all present PCI devices
> > > +     */
> > > +    if (pdev->acpi_index) {
> > > +        GSequence *used_indexes = pci_acpi_index_list();
> > > +
> > > +        if (g_sequence_lookup(used_indexes, 
> > > GINT_TO_POINTER(pdev->acpi_index),
> > > +                              g_cmp_uint32, NULL)) {
> > > +            error_setg(errp, "a PCI device with acpi-index = %" PRIu32
> > > +                       " already exist", pdev->acpi_index);
> > > +            return;
> > > +        }
> > > +        g_sequence_insert_sorted(used_indexes,
> > > +                                 GINT_TO_POINTER(pdev->acpi_index),
> > > +                                 g_cmp_uint32, NULL);
> > > +    }  
> > 
> > This doesn't appear to ensure uniqueness when using PCIe topologies:
> > 
> > $ ./build/x86_64-softmmu/qemu-system-x86_64 \
> >      -device virtio-net,acpi-index=100 \
> >      -device virtio-net,acpi-index=100
> > qemu-system-x86_64: -device virtio-net,acpi-index=100: a PCI device with 
> > acpi-index = 100 already exist
> > 
> > $ ./build/x86_64-softmmu/qemu-system-x86_64 \
> >      -M q35 \
> >      -device virtio-net,acpi-index=100
> >      -device virtio-net,acpi-index=100
> > ....happily running....  
> 
> In fact the entire concept doesn't appear to work with Q35 at all as
> implemented.
> 
> The 'acpi_index' file in the guest OS never gets created and the NICs
> are still called 'eth0', 'eth1'
> 
> Only with i440fx can I can the "enoNNN" based naming to work with
> acpi-index set from QEMU

It is not supported on Q35 yet as it depends on ACPI PCI hotplug infrastructure.
Once Julia is done with porting it to Q35, acpi-index will be pulled along with 
it.


> Regards,
> Daniel