Re: [PATCH v15 15/60] i386/xen: add pc_machine_kvm_type to initialize XEN_EMULATE mode

[Xiaoyao Li]

On 3/1/2023 9:51 PM, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
>
> The xen_overlay device (and later similar devices for event channels and
> grant tables) need to be instantiated. Do this from a kvm_type method on
> the PC machine derivatives, since KVM is only way to support Xen emulation
> for now.

Just curious, isn't there any more reasonable place to add machine 
specific initialization?

abusing the mc->kvm_type() looks bad to me.

If everything goes well, KVM x86 will support multiple vm_type[1].
At that time, QEMU will need to implement mc->kvm_type() to get/parse vm 
type. I have posted the patch to enable it for TDX[2].

[1] 
https://github.com/sean-jc/linux/commit/fbc35ac0be99b5e02248e7c8f1f3cacb9da512ce

[2] 
https://lore.kernel.org/qemu-devel/20220802074750.2581308-4-xiaoyao.li@intel.com/ 


> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> Reviewed-by: Paul Durrant <paul@xen.org>
> ---
>   hw/i386/pc.c         | 11 +++++++++++
>   include/hw/i386/pc.h |  3 +++
>   2 files changed, 14 insertions(+)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 992951c107..a316a01b15 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -90,6 +90,7 @@
>   #include "hw/virtio/virtio-iommu.h"
>   #include "hw/virtio/virtio-pmem-pci.h"
>   #include "hw/virtio/virtio-mem-pci.h"
> +#include "hw/i386/kvm/xen_overlay.h"
>   #include "hw/mem/memory-device.h"
>   #include "sysemu/replay.h"
>   #include "target/i386/cpu.h"
> @@ -1846,6 +1847,16 @@ static void pc_machine_initfn(Object *obj)
>       cxl_machine_init(obj, &pcms->cxl_devices_state);
>   }
>   
> +int pc_machine_kvm_type(MachineState *machine, const char *kvm_type)
> +{
> +#ifdef CONFIG_XEN_EMU
> +    if (xen_mode == XEN_EMULATE) {
> +        xen_overlay_create();
> +    }
> +#endif
> +    return 0;
> +}
> +
>   static void pc_machine_reset(MachineState *machine, ShutdownCause reason)
>   {
>       CPUState *cs;
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 66e3d059ef..467311007e 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -291,12 +291,15 @@ extern const size_t pc_compat_1_5_len;
>   extern GlobalProperty pc_compat_1_4[];
>   extern const size_t pc_compat_1_4_len;
>   
> +int pc_machine_kvm_type(MachineState *machine, const char *vm_type);
> +
>   #define DEFINE_PC_MACHINE(suffix, namestr, initfn, optsfn) \
>       static void pc_machine_##suffix##_class_init(ObjectClass *oc, void *data) 
> \
>       { \
>           MachineClass *mc = MACHINE_CLASS(oc); \
>           optsfn(mc); \
>           mc->init = initfn; \
> +        mc->kvm_type = pc_machine_kvm_type; \
>       } \
>       static const TypeInfo pc_machine_type_##suffix = { \
>           .name       = namestr TYPE_MACHINE_SUFFIX, \