Re: [Qemu-devel] [PATCH] Remove PCI class code from virtio balloon device

[David Gibson <dwg@au1.ibm.com>]

Anthony..

please apply?

On Mon, Mar 26, 2012 at 12:19:40PM +1100, David Gibson wrote:
> Currently the virtio balloon device, when using the virtio-pci interface
> advertises itself with PCI class code MEMORY_RAM.  This is wrong; the
> balloon is vaguely related to memory, but is nothing like a PCI memory
> device in the meaning of the class code, and this code is not required or
> suggested by the virtio PCI specification.
> 
> Worse, this patch causes problems on the pseries machine, because the
> firmware, seeing this class code, advertises the device as memory in the
> device tree, and then a guest kernel bug causes it to see this "memory"
> before the real system memory, leading to a crash in early boot.
> 
> This patch fixes the problem by removing the bogus PCI class code on the
> balloon device.  The backwards compatibility PC machines get new compat
> properties so that they don't change.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/pc_piix.c    |   28 ++++++++++++++++++++++++++++
>  hw/virtio-pci.c |    8 +++++++-
>  2 files changed, 35 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 3f99f9a..55dcd2e 100644
> --- a/hw/pc_piix.c
> +++ b/hw/pc_piix.c
> @@ -386,6 +386,10 @@ static QEMUMachine pc_machine_v1_0 = {
>              .driver   = "isa-fdc",
>              .property = "check_media_rate",
>              .value    = "off",
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      },
> @@ -405,6 +409,10 @@ static QEMUMachine pc_machine_v0_15 = {
>              .driver   = "isa-fdc",
>              .property = "check_media_rate",
>              .value    = "off",
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      },
> @@ -449,6 +457,10 @@ static QEMUMachine pc_machine_v0_14 = {
>              .driver   = "pc-sysfw",
>              .property = "rom_only",
>              .value    = stringify(1),
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      },
> @@ -505,6 +517,10 @@ static QEMUMachine pc_machine_v0_13 = {
>              .driver   = "pc-sysfw",
>              .property = "rom_only",
>              .value    = stringify(1),
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      },
> @@ -565,6 +581,10 @@ static QEMUMachine pc_machine_v0_12 = {
>              .driver   = "pc-sysfw",
>              .property = "rom_only",
>              .value    = stringify(1),
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      }
> @@ -633,6 +653,10 @@ static QEMUMachine pc_machine_v0_11 = {
>              .driver   = "pc-sysfw",
>              .property = "rom_only",
>              .value    = stringify(1),
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      }
> @@ -713,6 +737,10 @@ static QEMUMachine pc_machine_v0_10 = {
>              .driver   = "pc-sysfw",
>              .property = "rom_only",
>              .value    = stringify(1),
> +        }, {
> +            .driver   = "virtio-balloon-pci",
> +            .property = "class",
> +            .value    = stringify(PCI_CLASS_MEMORY_RAM),
>          },
>          { /* end of list */ }
>      },
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index a0fb7c1..a1fa656 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -790,6 +790,11 @@ static int virtio_balloon_init_pci(PCIDevice *pci_dev)
>      VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
>      VirtIODevice *vdev;
>  
> +    if (proxy->class_code != PCI_CLASS_OTHERS &&
> +        proxy->class_code != PCI_CLASS_MEMORY_RAM) { /* qemu < 1.1 */
> +        proxy->class_code = PCI_CLASS_OTHERS;
> +    }
> +
>      vdev = virtio_balloon_init(&pci_dev->qdev);
>      if (!vdev) {
>          return -1;
> @@ -905,6 +910,7 @@ static TypeInfo virtio_serial_info = {
>  };
>  
>  static Property virtio_balloon_properties[] = {
> +    DEFINE_PROP_HEX32("class", VirtIOPCIProxy, class_code, PCI_CLASS_OTHERS),
>      DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
>      DEFINE_PROP_END_OF_LIST(),
>  };
> @@ -919,7 +925,7 @@ static void virtio_balloon_class_init(ObjectClass *klass, void *data)
>      k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
>      k->device_id = PCI_DEVICE_ID_VIRTIO_BALLOON;
>      k->revision = VIRTIO_PCI_ABI_VERSION;
> -    k->class_id = PCI_CLASS_MEMORY_RAM;
> +    k->class_id = PCI_CLASS_OTHERS;
>      dc->reset = virtio_pci_reset;
>      dc->props = virtio_balloon_properties;
>  }

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson