entry: temporarily disable interrupt nesting

We play with the tss, which is supposedly per-cpu, but this has not been
implemented yet.  Disable it temporarily.  Meanwhile, interrupts and
exceptions may not nest.

arch/x64/entry.S

 
 #include "cfi.S"
 
-interrupt_stack_frame = 4096
-
 .macro exception_entry name, handler, has_error_code
 	.global \name
 	\name :
@@ -14,7 +12,6 @@ interrupt_stack_frame = 4096
 	.cfi_def_cfa %rsp, 0
 	.cfi_offset %rip, 8
 	.cfi_offset %rsp, 32
-	subq $interrupt_stack_frame, tss_ist+8 # FIXME: assumes proper nesting of interrupts
 	pushq_cfi %rax
 	pushq_cfi %rbx
 	pushq_cfi %rcx
@@ -48,7 +45,6 @@ interrupt_stack_frame = 4096
 	popq_cfi %rbx
 	popq_cfi %rax
 	add $8, %rsp
-	addq $interrupt_stack_frame, tss_ist+8 # FIXME: assumes proper nesting of interrupts
 	iretq
 	.cfi_endproc
 .endm