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 
enter_vmx_usercopy(void)13 int 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  */
exit_vmx_usercopy(void)35 int 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 
enter_vmx_ops(void)53 int 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  */
exit_vmx_ops(void * dest)70 void *exit_vmx_ops(void *dest)
71 {
72 	disable_kernel_altivec();
73 	preempt_enable();
74 	return dest;
75 }
76