1/*
2 * Copyright (C) 2012,2013 - ARM Ltd
3 * Author: Marc Zyngier <marc.zyngier@arm.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
16 */
17
18#include <linux/linkage.h>
19
20#include <asm/alternative.h>
21#include <asm/assembler.h>
22#include <asm/cpufeature.h>
23
24/*
25 * u64 __kvm_call_hyp(void *hypfn, ...);
26 *
27 * This is not really a variadic function in the classic C-way and care must
28 * be taken when calling this to ensure parameters are passed in registers
29 * only, since the stack will change between the caller and the callee.
30 *
31 * Call the function with the first argument containing a pointer to the
32 * function you wish to call in Hyp mode, and subsequent arguments will be
33 * passed as x0, x1, and x2 (a maximum of 3 arguments in addition to the
34 * function pointer can be passed).  The function being called must be mapped
35 * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
36 * passed in x0.
37 *
38 * A function pointer with a value less than 0xfff has a special meaning,
39 * and is used to implement hyp stubs in the same way as in
40 * arch/arm64/kernel/hyp_stub.S.
41 */
42ENTRY(__kvm_call_hyp)
43alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
44	hvc	#0
45	ret
46alternative_else_nop_endif
47	b	__vhe_hyp_call
48ENDPROC(__kvm_call_hyp)
49