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

["Daniel P. Berrangé" <berrange@redhat.com>]

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....


Regards,
Daniel
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