Re: [Qemu-devel] [RFC PATCH 16/30] q35/xen: Add Xen platform device support for Q35

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

On Tue, Mar 13, 2018 at 04:34:01AM +1000, Alexey Gerasimenko wrote:
> Current Xen/QEMU method to control Xen Platform device on i440 is a bit
> odd -- enabling/disabling Xen platform device actually modifies the QEMU
> emulated machine type, namely xenfv <--> pc.
> 
> In order to avoid multiplying machine types, use a new way to control Xen
> Platform device for QEMU -- "xen-platform-dev" machine property (bool).
> To maintain backward compatibility with existing Xen/QEMU setups, this
> is only applicable to q35 machine currently. i440 emulation still uses the
> old method (i.e. xenfv/pc machine selection) to control Xen Platform
> device, this may be changed later to xen-platform-dev property as well.

The change you made to q35 is pretty tiny, so I imagine the equiv
change to pc machine is equally small. IOW, I think you should just
convert them both straight away rather than providing an inconsistent
configuration approach for q35 vs pc.

> This way we can use a single machine type (q35) and change just
> xen-platform-dev value to on/off to control Xen platform device.
> 
> Signed-off-by: Alexey Gerasimenko <x1917x@gmail.com>
> ---
>  hw/core/machine.c   | 21 +++++++++++++++++++++
>  hw/i386/pc_q35.c    | 14 ++++++++++++++
>  include/hw/boards.h |  1 +
>  qemu-options.hx     |  1 +
>  4 files changed, 37 insertions(+)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 5e2bbcdace..205e7da3ce 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -290,6 +290,20 @@ static void machine_set_igd_gfx_passthru(Object *obj, bool value, Error **errp)
>      ms->igd_gfx_passthru = value;
>  }
>  
> +static bool machine_get_xen_platform_dev(Object *obj, Error **errp)
> +{
> +    MachineState *ms = MACHINE(obj);
> +
> +    return ms->xen_platform_dev;
> +}
> +
> +static void machine_set_xen_platform_dev(Object *obj, bool value, Error **errp)
> +{
> +    MachineState *ms = MACHINE(obj);
> +
> +    ms->xen_platform_dev = value;
> +}
> +
>  static char *machine_get_firmware(Object *obj, Error **errp)
>  {
>      MachineState *ms = MACHINE(obj);
> @@ -595,6 +609,13 @@ static void machine_class_init(ObjectClass *oc, void *data)
>      object_class_property_set_description(oc, "igd-passthru",
>          "Set on/off to enable/disable igd passthrou", &error_abort);
>  
> +    object_class_property_add_bool(oc, "xen-platform-dev",
> +        machine_get_xen_platform_dev,
> +        machine_set_xen_platform_dev, &error_abort);
> +    object_class_property_set_description(oc, "xen-platform-dev",
> +        "Set on/off to enable/disable Xen Platform device",
> +        &error_abort);
> +
>      object_class_property_add_str(oc, "firmware",
>          machine_get_firmware, machine_set_firmware,
>          &error_abort);
> diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> index 0db670f6d7..62caf924cf 100644
> --- a/hw/i386/pc_q35.c
> +++ b/hw/i386/pc_q35.c
> @@ -56,6 +56,18 @@
>  /* ICH9 AHCI has 6 ports */
>  #define MAX_SATA_PORTS     6
>  
> +static void q35_xen_hvm_init(MachineState *machine)
> +{
> +    PCMachineState *pcms = PC_MACHINE(machine);
> +
> +    if (xen_enabled()) {
> +        /* check if Xen Platform device is enabled */
> +        if (machine->xen_platform_dev) {
> +            pci_create_simple(pcms->bus, -1, "xen-platform");
> +        }
> +    }
> +}
> +
>  /* PC hardware initialisation */
>  static void pc_q35_init(MachineState *machine)
>  {
> @@ -207,6 +219,8 @@ static void pc_q35_init(MachineState *machine)
>      if (xen_enabled()) {
>          pci_bus_irqs(host_bus, xen_cmn_set_irq, xen_cmn_pci_slot_get_pirq,
>                       ich9_lpc, ICH9_XEN_NUM_IRQ_SOURCES);
> +
> +        q35_xen_hvm_init(machine);
>      } else {
>          pci_bus_irqs(host_bus, ich9_lpc_set_irq, ich9_lpc_map_irq, ich9_lpc,
>                       ICH9_LPC_NB_PIRQS);
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index efb0a9edfd..f35fc1cc03 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -238,6 +238,7 @@ struct MachineState {
>      bool usb;
>      bool usb_disabled;
>      bool igd_gfx_passthru;
> +    bool xen_platform_dev;
>      char *firmware;
>      bool iommu;
>      bool suppress_vmdesc;
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 6585058c6c..cee0b92028 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -38,6 +38,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>      "                dump-guest-core=on|off include guest memory in a core dump (default=on)\n"
>      "                mem-merge=on|off controls memory merge support (default: on)\n"
>      "                igd-passthru=on|off controls IGD GFX passthrough support (default=off)\n"
> +    "                xen-platform-dev=on|off controls Xen Platform device (default=off)\n"
>      "                aes-key-wrap=on|off controls support for AES key wrapping (default=on)\n"
>      "                dea-key-wrap=on|off controls support for DEA key wrapping (default=on)\n"
>      "                suppress-vmdesc=on|off disables self-describing migration (default=off)\n"
> -- 
> 2.11.0
> 
> 

Regards,
Daniel
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