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
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 */
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
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 */
70 void *exit_vmx_ops(void *dest)
71 {
72 disable_kernel_altivec();
73 preempt_enable();
74 return dest;
75 }
76
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