Re: [Qemu-devel] [PATCH] Fix pc migration from qemu <= 1.5

[Bandan Das <bsd@redhat.com>]

Hi Cole,

Cole Robinson <crobinso@redhat.com> writes:

> The following commit introduced a migration incompatibility:
>
> commit 568f0690fd9aa4d39d84b04c1a5dbb53a915c3fe
> Author: David Gibson <david@gibson.dropbear.id.au>
> Date:   Thu Jun 6 18:48:49 2013 +1000
>
>     pci: Replace pci_find_domain() with more general pci_root_bus_path()
>
> The issue is that i440fx savevm idstr went from 0000:00:00.0/I440FX to
> 0000:00.0/I440FX. Unfortunately we are stuck with the breakage for
> 1.6 machine types.
>
> Add a compat property to maintain the busted idstr for the 1.6 machine
> types, but revert to the old style format for 1.7+, and <= 1.5.
>
> Tested with migration from qemu 1.5, qemu 1.6, and qemu.git.
>
> Signed-off-by: Cole Robinson <crobinso@redhat.com>
> ---
>  hw/i386/pc_piix.c         |  4 ++++
>  hw/i386/pc_q35.c          |  4 ++++
>  hw/pci-host/piix.c        |  9 ++++++++-
>  hw/pci-host/q35.c         | 10 ++++++++--
>  include/hw/i386/pc.h      | 28 ++++++++++++++++++++++++++++
>  include/hw/pci-host/q35.h |  1 +
>  6 files changed, 53 insertions(+), 3 deletions(-)
>
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index c6042c7..90f1ea4 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -346,6 +346,10 @@ static QEMUMachine pc_i440fx_machine_v1_7 = {
>      .alias = "pc",
>      .init = pc_init_pci,
>      .is_default = 1,
> +    .compat_props = (GlobalProperty[]) {
> +        PC_COMPAT_1_7,
> +        { /* end of list */ }
> +    },
>  };  
>  #define PC_I440FX_1_6_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index ca84e1c..569f946 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -270,6 +270,10 @@ static QEMUMachine pc_q35_machine_v1_7 = {
>      .name = "pc-q35-1.7",
>      .alias = "q35",
>      .init = pc_q35_init,
> +    .compat_props = (GlobalProperty[]) {
> +        PC_COMPAT_1_7,
> +        { /* end of list */ }
> +    },
>  };
>  #define PC_Q35_1_6_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index c041149..9dafe80 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -48,6 +48,7 @@ typedef struct I440FXState {
>      PCIHostState parent_obj;
>      PcPciInfo pci_info;
>      uint64_t pci_hole64_size;
> +    uint32_t short_root_bus;
>  } I440FXState;
>  
>  #define PIIX_NUM_PIC_IRQS       16      /* i8259 * 2 */
> @@ -712,13 +713,19 @@ static const TypeInfo i440fx_info = {
>  static const char *i440fx_pcihost_root_bus_path(PCIHostState *host_bridge,
>                                                  PCIBus *rootbus)
>  {
> +    I440FXState *s = I440FX_PCI_HOST_BRIDGE(host_bridge);
> +
>      /* For backwards compat with old device paths */
> -    return "0000";
> +    if (s->short_root_bus) {
> +        return "0000";
> +    }
> +    return "0000:00";
>  }
>  
>  static Property i440fx_props[] = {
>      DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, I440FXState,
>                       pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
> +    DEFINE_PROP_UINT32("short_root_bus", I440FXState, short_root_bus, 0),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
> index ad703a4..cb3abfd 100644
> --- a/hw/pci-host/q35.c
> +++ b/hw/pci-host/q35.c
> @@ -61,8 +61,13 @@ static void q35_host_realize(DeviceState *dev, Error **errp)
>  static const char *q35_host_root_bus_path(PCIHostState *host_bridge,
>                                            PCIBus *rootbus)
>  {
> -    /* For backwards compat with old device paths */
> -    return "0000";
> +    Q35PCIHost *s = Q35_HOST_DEVICE(host_bridge);
> +
> +     /* For backwards compat with old device paths */
> +    if (s->mch.short_root_bus) {
> +        return "0000";
> +    }
> +    return "0000:00";
>  }
>  
>  static void q35_host_get_pci_hole_start(Object *obj, Visitor *v,
> @@ -114,6 +119,7 @@ static Property mch_props[] = {
>                          MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT),
>      DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, Q35PCIHost,
>                       mch.pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
> +    DEFINE_PROP_UINT32("short_root_bus", Q35PCIHost, mch.short_root_bus, 0),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 9b2ddc4..f9266f0 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -225,11 +225,31 @@ void pvpanic_init(ISABus *bus);
>  
>  int e820_add_entry(uint64_t, uint64_t, uint32_t);
>  
> +#define PC_COMPAT_1_7 \
> +        {\
> +            .driver   = "i440FX-pcihost",\
> +            .property = "short_root_bus",\
> +            .value    = stringify(0),\
> +        },{\
> +            .driver   = "mch",\
> +            .property = "short_root_bus",\
> +            .value    = stringify(0),\
> +        }
> +

This is probably not needed since the default value of 
short_root_bus is already 0. BTW, 1_7 shouldn't have 
compat props since  it's already the most uptodate 
machine type and by definition, compat properties only apply
to older machine types.

Bandan

>  #define PC_COMPAT_1_6 \
> +        PC_COMPAT_1_7, \
>          {\
>              .driver   = "e1000",\
>              .property = "mitigation",\
>              .value    = "off",\
> +        },{\
> +            .driver   = "i440FX-pcihost",\
> +            .property = "short_root_bus",\
> +            .value    = stringify(1),\
> +        },{\
> +            .driver   = "mch",\
> +            .property = "short_root_bus",\
> +            .value    = stringify(1),\
>          }
>  
>  #define PC_COMPAT_1_5 \
> @@ -266,6 +286,14 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
>              .driver = TYPE_X86_CPU,\
>              .property = "pmu",\
>              .value = "on",\
> +        },{\
> +            .driver   = "i440FX-pcihost",\
> +            .property = "short_root_bus",\
> +            .value    = stringify(0),\
> +        },{\
> +            .driver   = "mch",\
> +            .property = "short_root_bus",\
> +            .value    = stringify(0),\
>          }
>  
>  #define PC_COMPAT_1_4 \
> diff --git a/include/hw/pci-host/q35.h b/include/hw/pci-host/q35.h
> index 56de92e..c8362b9 100644
> --- a/include/hw/pci-host/q35.h
> +++ b/include/hw/pci-host/q35.h
> @@ -61,6 +61,7 @@ typedef struct MCHPCIState {
>      ram_addr_t above_4g_mem_size;
>      uint64_t pci_hole64_size;
>      PcGuestInfo *guest_info;
> +    uint32_t short_root_bus;
>  } MCHPCIState;
>  
>  typedef struct Q35PCIHost {