| 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
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| 2 | /* |
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| 3 | * |
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| 4 | * Copyright (C) IBM Corporation, 2011 |
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| 5 | * |
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| 6 | * Authors: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> |
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| 7 | * Anton Blanchard <anton@au.ibm.com> |
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| 8 | */ |
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| 9 | #include <linux/uaccess.h> |
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| 10 | #include <linux/hardirq.h> |
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| 11 | #include <asm/switch_to.h> |
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| 12 | |
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| 13 | int enter_vmx_usercopy(void) |
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| 14 | { |
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| 15 | if (in_interrupt()) |
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| 16 | return 0; |
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| 17 | |
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| 18 | preempt_disable(); |
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| 19 | /* |
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| 20 | * We need to disable page faults as they can call schedule and |
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| 21 | * thus make us lose the VMX context. So on page faults, we just |
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| 22 | * fail which will cause a fallback to the normal non-vmx copy. |
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| 23 | */ |
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| 24 | pagefault_disable(); |
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| 25 | |
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| 26 | enable_kernel_altivec(); |
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| 27 | |
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| 28 | return 1; |
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| 29 | } |
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| 30 | |
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| 31 | /* |
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| 32 | * This function must return 0 because we tail call optimise when calling |
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| 33 | * from __copy_tofrom_user_power7 which returns 0 on success. |
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| 34 | */ |
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| 35 | int exit_vmx_usercopy(void) |
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| 36 | { |
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| 37 | disable_kernel_altivec(); |
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| 38 | pagefault_enable(); |
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| 39 | preempt_enable_no_resched(); |
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| 40 | /* |
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| 41 | * Must never explicitly call schedule (including preempt_enable()) |
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| 42 | * while in a kuap-unlocked user copy, because the AMR register will |
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| 43 | * not be saved and restored across context switch. However preempt |
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| 44 | * kernels need to be preempted as soon as possible if need_resched is |
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| 45 | * set and we are preemptible. The hack here is to schedule a |
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| 46 | * decrementer to fire here and reschedule for us if necessary. |
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| 47 | */ |
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| 48 | if (IS_ENABLED(CONFIG_PREEMPT) && need_resched()) |
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| 49 | set_dec(1); |
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| 50 | return 0; |
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| 51 | } |
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| 52 | |
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| 53 | int enter_vmx_ops(void) |
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| 54 | { |
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| 55 | if (in_interrupt()) |
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| 56 | return 0; |
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| 57 | |
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| 58 | preempt_disable(); |
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| 59 | |
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| 60 | enable_kernel_altivec(); |
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| 61 | |
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| 62 | return 1; |
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| 63 | } |
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| 64 | |
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| 65 | /* |
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| 66 | * All calls to this function will be optimised into tail calls. We are |
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| 67 | * passed a pointer to the destination which we return as required by a |
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| 68 | * memcpy implementation. |
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| 69 | */ |
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| 70 | void *exit_vmx_ops(void *dest) |
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| 71 | { |
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| 72 | disable_kernel_altivec(); |
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| 73 | preempt_enable(); |
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| 74 | return dest; |
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| 75 | } |
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| 76 | |
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