// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) IBM Corporation, 2011
 *
 * Authors: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
 *          Anton Blanchard <anton@au.ibm.com>
 */
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <asm/switch_to.h>

int enter_vmx_usercopy(void)
{
        if (in_interrupt())
                return 0;

        preempt_disable();
        /*
         * We need to disable page faults as they can call schedule and
         * thus make us lose the VMX context. So on page faults, we just
         * fail which will cause a fallback to the normal non-vmx copy.
         */
        pagefault_disable();

        enable_kernel_altivec();

        return 1;
}
EXPORT_SYMBOL(enter_vmx_usercopy);

/*
 * This function must return 0 because we tail call optimise when calling
 * from __copy_tofrom_user_power7 which returns 0 on success.
 */
int exit_vmx_usercopy(void)
{
        disable_kernel_altivec();
        pagefault_enable();
        preempt_enable_no_resched();
        /*
         * Must never explicitly call schedule (including preempt_enable())
         * while in a kuap-unlocked user copy, because the AMR register will
         * not be saved and restored across context switch. However preempt
         * kernels need to be preempted as soon as possible if need_resched is
         * set and we are preemptible. The hack here is to schedule a
         * decrementer to fire here and reschedule for us if necessary.
         */
        if (need_irq_preemption() && need_resched())
                set_dec(1);
        return 0;
}
EXPORT_SYMBOL(exit_vmx_usercopy);

int enter_vmx_ops(void)
{
        if (in_interrupt())
                return 0;

        preempt_disable();

        enable_kernel_altivec();

        return 1;
}

/*
 * All calls to this function will be optimised into tail calls. We are
 * passed a pointer to the destination which we return as required by a
 * memcpy implementation.
 */
void *exit_vmx_ops(void *dest)
{
        disable_kernel_altivec();
        preempt_enable();
        return dest;
}