On Wed, Jul 28, 2021 at 10:52:21AM -0400, Tianyu Lan wrote: > + hv_ghcb->ghcb.protocol_version = 1; > + hv_ghcb->ghcb.ghcb_usage = 1; The values set to ghcb_usage deserve some defines (here and below). > + > + hv_ghcb->hypercall.outputgpa = (u64)output; > + hv_ghcb->hypercall.hypercallinput.asuint64 = 0; > + hv_ghcb->hypercall.hypercallinput.callcode = control; > + > + if (input_size) > + memcpy(hv_ghcb->hypercall.hypercalldata, input, input_size); > + > + VMGEXIT(); > + > + hv_ghcb->ghcb.ghcb_usage = 0xffffffff; ... > union hv_ghcb { > struct ghcb ghcb; > + struct { > + u64 hypercalldata[509]; > + u64 outputgpa; > + union { > + union { > + struct { > + u32 callcode : 16; > + u32 isfast : 1; > + u32 reserved1 : 14; > + u32 isnested : 1; > + u32 countofelements : 12; > + u32 reserved2 : 4; > + u32 repstartindex : 12; > + u32 reserved3 : 4; > + }; > + u64 asuint64; > + } hypercallinput; > + union { > + struct { > + u16 callstatus; > + u16 reserved1; > + u32 elementsprocessed : 12; > + u32 reserved2 : 20; > + }; > + u64 asunit64; > + } hypercalloutput; > + }; > + u64 reserved2; > + } hypercall; Okay, this answers my previous question :)