/*
 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
 * Author: Christoffer Dall <c.dall@virtualopensystems.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#include <linux/kvm_host.h>
#include <asm/kvm_mmio.h>
#include <asm/kvm_emulate.h>
#include <trace/events/kvm.h>

#include "trace.h"

static void mmio_write_buf(char *buf, unsigned int len, unsigned long data)
{
        void *datap = NULL;
        union {
                u8      byte;
                u16     hword;
                u32     word;
                u64     dword;
        } tmp;

        switch (len) {
        case 1:
                tmp.byte        = data;
                datap           = &tmp.byte;
                break;
        case 2:
                tmp.hword       = data;
                datap           = &tmp.hword;
                break;
        case 4:
                tmp.word        = data;
                datap           = &tmp.word;
                break;
        case 8:
                tmp.dword       = data;
                datap           = &tmp.dword;
                break;
        }

        memcpy(buf, datap, len);
}

static unsigned long mmio_read_buf(char *buf, unsigned int len)
{
        unsigned long data = 0;
        union {
                u16     hword;
                u32     word;
                u64     dword;
        } tmp;

        switch (len) {
        case 1:
                data = buf[0];
                break;
        case 2:
                memcpy(&tmp.hword, buf, len);
                data = tmp.hword;
                break;
        case 4:
                memcpy(&tmp.word, buf, len);
                data = tmp.word;
                break;
        case 8:
                memcpy(&tmp.dword, buf, len);
                data = tmp.dword;
                break;
        }

        return data;
}

/**
 * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
 * @vcpu: The VCPU pointer
 * @run:  The VCPU run struct containing the mmio data
 *
 * This should only be called after returning from userspace for MMIO load
 * emulation.
 */
int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        unsigned long data;
        unsigned int len;
        int mask;

        if (!run->mmio.is_write) {
                len = run->mmio.len;
                if (len > sizeof(unsigned long))
                        return -EINVAL;

                data = mmio_read_buf(run->mmio.data, len);

                if (vcpu->arch.mmio_decode.sign_extend &&
                    len < sizeof(unsigned long)) {
                        mask = 1U << ((len * 8) - 1);
                        data = (data ^ mask) - mask;
                }

                trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
                               data);
                data = vcpu_data_host_to_guest(vcpu, data, len);
                vcpu_set_reg(vcpu, vcpu->arch.mmio_decode.rt, data);
        }

        return 0;
}

static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len)
{
        unsigned long rt;
        int access_size;
        bool sign_extend;

        if (kvm_vcpu_dabt_isextabt(vcpu)) {
                /* cache operation on I/O addr, tell guest unsupported */
                kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
                return 1;
        }

        if (kvm_vcpu_dabt_iss1tw(vcpu)) {
                /* page table accesses IO mem: tell guest to fix its TTBR */
                kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
                return 1;
        }

        access_size = kvm_vcpu_dabt_get_as(vcpu);
        if (unlikely(access_size < 0))
                return access_size;

        *is_write = kvm_vcpu_dabt_iswrite(vcpu);
        sign_extend = kvm_vcpu_dabt_issext(vcpu);
        rt = kvm_vcpu_dabt_get_rd(vcpu);

        *len = access_size;
        vcpu->arch.mmio_decode.sign_extend = sign_extend;
        vcpu->arch.mmio_decode.rt = rt;

        /*
         * The MMIO instruction is emulated and should not be re-executed
         * in the guest.
         */
        kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
        return 0;
}

int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
                 phys_addr_t fault_ipa)
{
        unsigned long data;
        unsigned long rt;
        int ret;
        bool is_write;
        int len;
        u8 data_buf[8];

        /*
         * Prepare MMIO operation. First decode the syndrome data we get
         * from the CPU. Then try if some in-kernel emulation feels
         * responsible, otherwise let user space do its magic.
         */
        if (kvm_vcpu_dabt_isvalid(vcpu)) {
                ret = decode_hsr(vcpu, &is_write, &len);
                if (ret)
                        return ret;
        } else {
                kvm_err("load/store instruction decoding not implemented\n");
                return -ENOSYS;
        }

        rt = vcpu->arch.mmio_decode.rt;

        if (is_write) {
                data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
                                               len);

                trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, data);
                mmio_write_buf(data_buf, len, data);

                ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len,
                                       data_buf);
        } else {
                trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len,
                               fault_ipa, 0);

                ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len,
                                      data_buf);
        }

        /* Now prepare kvm_run for the potential return to userland. */
        run->mmio.is_write      = is_write;
        run->mmio.phys_addr     = fault_ipa;
        run->mmio.len           = len;
        if (is_write)
                memcpy(run->mmio.data, data_buf, len);

        if (!ret) {
                /* We handled the access successfully in the kernel. */
                vcpu->stat.mmio_exit_kernel++;
                kvm_handle_mmio_return(vcpu, run);
                return 1;
        } else {
                vcpu->stat.mmio_exit_user++;
        }

        run->exit_reason        = KVM_EXIT_MMIO;
        return 0;
}