GUID used to store the global debug mask value into an EFI Variable
Include/Guid/DebugMask.h

GUID Information

GUID's Guid Name	GUID's Guid
gEfiGenericVariableGuid	{ 0x59d1c24f, 0x50f1, 0x401a, {0xb1, 0x01, 0xf3, 0x3e, 0x0d, 0xae, 0xd4, 0x43} }

Refer to Header File