1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 *
 4 * Copyright (C) IBM Corporation, 2011
 5 *
 6 * Authors: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
 7 *          Anton Blanchard <anton@au.ibm.com>
 8 */
 9#include <linux/uaccess.h>
10#include <linux/hardirq.h>
11#include <asm/switch_to.h>
12
13int enter_vmx_usercopy(void)
14{
15	if (in_interrupt())
16		return 0;
17
18	preempt_disable();
19	/*
20	 * We need to disable page faults as they can call schedule and
21	 * thus make us lose the VMX context. So on page faults, we just
22	 * fail which will cause a fallback to the normal non-vmx copy.
23	 */
24	pagefault_disable();
25
26	enable_kernel_altivec();
27
28	return 1;
29}
30
31/*
32 * This function must return 0 because we tail call optimise when calling
33 * from __copy_tofrom_user_power7 which returns 0 on success.
34 */
35int exit_vmx_usercopy(void)
36{
37	disable_kernel_altivec();
38	pagefault_enable();
39	preempt_enable_no_resched();
40	/*
41	 * Must never explicitly call schedule (including preempt_enable())
42	 * while in a kuap-unlocked user copy, because the AMR register will
43	 * not be saved and restored across context switch. However preempt
44	 * kernels need to be preempted as soon as possible if need_resched is
45	 * set and we are preemptible. The hack here is to schedule a
46	 * decrementer to fire here and reschedule for us if necessary.
47	 */
48	if (IS_ENABLED(CONFIG_PREEMPT) && need_resched())
49		set_dec(1);
50	return 0;
51}
52
53int enter_vmx_ops(void)
54{
55	if (in_interrupt())
56		return 0;
57
58	preempt_disable();
59
60	enable_kernel_altivec();
61
62	return 1;
63}
64
65/*
66 * All calls to this function will be optimised into tail calls. We are
67 * passed a pointer to the destination which we return as required by a
68 * memcpy implementation.
69 */
70void *exit_vmx_ops(void *dest)
71{
72	disable_kernel_altivec();
73	preempt_enable();
74	return dest;
75}