Re: [Xen-devel] [PATCH v3 8/8] RFC: Sketch constructors, DomainCreateNew

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 1/17/20 3:57 PM, George Dunlap wrote:
> This is a sketch of functionality suitable for creating a basic
> domain, with a disk and a vif.  DomainConfig, DeviceDisk, and
> DeviceNic types are all created using constructor functions, which
> initialize them with libxl's defaults.
> 
> DomainCreateNew takes the config and calls without any updates.
> 
> Obviously some of these will need to be changed it we switch to
> passing references to .toC() rather than passing back by value.
> 
> The main purpose of this is to allow testing of creating a hard-coded
> domain.
> 
> Creating a domain would look like this:
> 
>       // type = "pv"
>       dconf, err := xl.NewDomainConfig(xl.DomainTypePv)
>       if err != nil {
>               fmt.Printf("NewDomainConfig: %v\n", err)
>               return
>       }
>       dconf.CInfo.Type = xl.DomainTypePv
>       // name = "c6-01"
>       dconf.CInfo.Name = "c6-01"
>       // vcpus=4
>       dconf.BInfo.MaxVcpus = 4
>       // memory = "2048"
>       dconf.BInfo.MaxMemkb = 2048 * 1024
>       dconf.BInfo.TargetMemkb = 2048 * 1024
>       // on_crash = 'destroy'
>       dconf.OnCrash = xl.ActionOnShutdownDestroy
>       // bootloader = "pygrub"
>       dconf.BInfo.Bootloader = "pygrub"
>       // disk = [ 'vdev=hda,format=raw,target=/images/c6-01.raw']
>       {
>               disk, err := xl.NewDeviceDisk()
>               if err != nil {
>                       fmt.Printf("NewDeviceDisk: %v\n", err)
>                       return
>               }
>               disk.Vdev = "hda"
>               //disk.DiskBackend = xl.DiskBackendPhy
>               disk.Format = xl.DiskFormatRaw
>               disk.Readwrite = 1
>               disk.PdevPath = "/images/c6-01.raw"
>               dconf.Disks = append(dconf.Disks, *disk)
>       }
>       // vif = [ 'mac=5a:5b:d6:f1:d6:b4' ]
>       {
>               vif, err := xl.NewDeviceNic()
>               if err != nil {
>                       fmt.Printf("NewDeviceNic: %v\n", err)
>                       return
>               }
>               vif.Mac = xl.Mac{ 0x5a, 0x5b, 0xd6, 0x31, 0xd6, 0xb4 }
>               dconf.Nics = append(dconf.Nics, *vif)
>       }
>       // serial='pty' # HVM only
> 
>       did, err := ctx.DomainCreateNew(dconf)
> 
>       if err != nil {
>               fmt.Printf("Creating domain: %v\n", err)
>               return
>       }
> 
>       fmt.Printf("Domain %s(%d) created successfully", dconf.CInfo.Name, did)
> 
> 
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> ---
> CC: Nick Rosbrook <rosbrookn@xxxxxxxxxxxx>
> ---
>  tools/golang/xenlight/xenlight.go | 66 +++++++++++++++++++++++++++++++
>  1 file changed, 66 insertions(+)
> 
> diff --git a/tools/golang/xenlight/xenlight.go 
> b/tools/golang/xenlight/xenlight.go
> index c462e4bb42..5a21a2b9b8 100644
> --- a/tools/golang/xenlight/xenlight.go
> +++ b/tools/golang/xenlight/xenlight.go
> @@ -1113,3 +1113,69 @@ func (Ctx *Context) PrimaryConsoleGetTty(domid uint32) 
> (path string, err error)
>       path = C.GoString(cpath)
>       return
>  }
> +
> +func NewDomainConfig(t DomainType) (*DomainConfig, error) {
> +     var cconfig C.libxl_domain_config
> +
> +     C.libxl_domain_config_init(&cconfig)
> +     C.libxl_domain_build_info_init_type(&cconfig.b_info, 
> C.libxl_domain_type(t))
> +
> +     gconfig := &DomainConfig{}
> +     err := gconfig.fromC(&cconfig)
> +     if err != nil {
> +             return nil, err
> +     }
> +
> +     return gconfig, nil
> +}
> +
> +func NewDeviceDisk() (*DeviceDisk, error) {
> +     var ctype C.libxl_device_disk
> +
> +     C.libxl_device_disk_init(&ctype)
> +
> +     gtype := &DeviceDisk{}
> +     err := gtype.fromC(&ctype)
> +
> +     if err != nil {
> +             return nil, err
> +     }
> +
> +     return gtype, nil
> +}
> +
> +func NewDeviceNic() (*DeviceNic, error) {
> +     var ctype C.libxl_device_nic
> +
> +     C.libxl_device_nic_init(&ctype)
> +
> +     gtype := &DeviceNic{}
> +     err := gtype.fromC(&ctype)
> +
> +     if err != nil {
> +             return nil, err
> +     }
> +
> +     return gtype, nil
> +}
> +
> +// int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
> +//                             uint32_t *domid,
> +//                             const libxl_asyncop_how *ao_how,
> +//                             const libxl_asyncprogress_how 
> *aop_console_how)
> +func (Ctx *Context) DomainCreateNew(config *DomainConfig) (Domid, error) {
> +     var cdomid C.uint32_t
> +     var cconfig C.libxl_domain_config
> +     err := config.toC(&cconfig)
> +     if err != nil {
> +             return Domid(0), fmt.Errorf("converting domain config to C: 
> %v", err)
> +     }
> +     defer C.libxl_domain_config_dispose(&cconfig)
> +
> +     ret := C.libxl_domain_create_new(Ctx.ctx, &cconfig, &cdomid, nil, nil)
> +     if ret != 0 {
> +             return Domid(0), Error(ret)
> +     }
> +
> +     return Domid(cdomid), nil
> +}

An alternate way to do this would be something like this:

---
func NewDomainConfig(t DomainType, populate func(*DomainConfig))
*DomainConfig {
        var ctype C.libxl_domain_config

        C.libxl_domain_config_init(&ctype)
        C.libxl_domain_build_info_init_type(&ctype.b_info, 
C.libxl_domain_type(t))

        gtype := &DomainConfig{}
        err := gtype.fromC(&ctype)
        if err != nil {
                panic("internal error: Can't convert empty DomainConfig")
        }

        if populate != nil {
                populate(gtype)
        }

        return gtype
}

func NewDeviceDisk(populate func(*DeviceDisk)) *DeviceDisk {
        var ctype C.libxl_device_disk

        C.libxl_device_disk_init(&ctype)

        gtype := &DeviceDisk{}
        err := gtype.fromC(&ctype)

        if err != nil {
                panic("internal error: Can't convert empty DeviceDisk")
        }

        if populate != nil {
                populate(gtype)
        }

        return gtype
}

func NewDeviceNic(populate func(*DeviceNic)) *DeviceNic {
        var ctype C.libxl_device_nic

        C.libxl_device_nic_init(&ctype)

        gtype := &DeviceNic{}
        err := gtype.fromC(&ctype)

        if err != nil {
                panic("internal error: Can't convert empty DeviceNic")
        }

        if populate != nil {
                populate(gtype)
        }

        return gtype
}
---

And then code to populate a domain config might look like this:

        dconf := xl.NewDomainConfig(xl.DomainTypePv, func(dconf 
*xl.DomainConfig) {
                dconf.CInfo.Type = xl.DomainTypePv
                // name = "c6-01"
                dconf.CInfo.Name = "c6-01"
                // vcpus=4
                dconf.BInfo.MaxVcpus = 4
                // memory = "2048"
                dconf.BInfo.MaxMemkb = 2048 * 1024
                dconf.BInfo.TargetMemkb = 2048 * 1024
                // on_crash = 'destroy'
                dconf.OnCrash = xl.ActionOnShutdownDestroy
                // bootloader = "pygrub"
                dconf.BInfo.Bootloader = "pygrub"
        })

        dconf.Disks = []xl.DeviceDisk{*xl.NewDeviceDisk(func(disk 
*xl.DeviceDisk) {
                disk.Vdev = "hda"
                //disk.DiskBackend = xl.DiskBackendPhy
                disk.Format = xl.DiskFormatRaw
                disk.Readwrite = 1
                disk.PdevPath = "/images/c6-01.raw"
                dconf.Disks = append(dconf.Disks, *disk)
        })}

        dconf.Nics = []xl.DeviceNic{*xl.NewDeviceNic(func(vif *xl.DeviceNic) {
                vif.Mac = xl.Mac{0x5a, 0x5b, 0xd6, 0x31, 0xd6, 0xb4}
        })}


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