/*
 * Copyright (C) 2012 - ARM Ltd
 * Author: Marc Zyngier <marc.zyngier@arm.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, see <http://www.gnu.org/licenses/>.
 */

#include <linux/preempt.h>
#include <linux/kvm_host.h>
#include <linux/wait.h>

#include <asm/cputype.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_psci.h>

/*
 * This is an implementation of the Power State Coordination Interface
 * as described in ARM document number ARM DEN 0022A.
 */

#define AFFINITY_MASK(level)    ~((0x1UL << ((level) * MPIDR_LEVEL_BITS)) - 1)

static unsigned long psci_affinity_mask(unsigned long affinity_level)
{
        if (affinity_level <= 3)
                return MPIDR_HWID_BITMASK & AFFINITY_MASK(affinity_level);

        return 0;
}

static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
{
        /*
         * NOTE: For simplicity, we make VCPU suspend emulation to be
         * same-as WFI (Wait-for-interrupt) emulation.
         *
         * This means for KVM the wakeup events are interrupts and
         * this is consistent with intended use of StateID as described
         * in section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
         *
         * Further, we also treat power-down request to be same as
         * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
         * specification (ARM DEN 0022A). This means all suspend states
         * for KVM will preserve the register state.
         */
        kvm_vcpu_block(vcpu);

        return PSCI_RET_SUCCESS;
}

static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
{
        vcpu->arch.pause = true;
}

static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
{
        struct kvm *kvm = source_vcpu->kvm;
        struct kvm_vcpu *vcpu = NULL, *tmp;
        wait_queue_head_t *wq;
        unsigned long cpu_id;
        unsigned long context_id;
        unsigned long mpidr;
        phys_addr_t target_pc;
        int i;

        cpu_id = *vcpu_reg(source_vcpu, 1);
        if (vcpu_mode_is_32bit(source_vcpu))
                cpu_id &= ~((u32) 0);

        kvm_for_each_vcpu(i, tmp, kvm) {
                mpidr = kvm_vcpu_get_mpidr(tmp);
                if ((mpidr & MPIDR_HWID_BITMASK) == (cpu_id & MPIDR_HWID_BITMASK)) {
                        vcpu = tmp;
                        break;
                }
        }

        /*
         * Make sure the caller requested a valid CPU and that the CPU is
         * turned off.
         */
        if (!vcpu)
                return PSCI_RET_INVALID_PARAMS;
        if (!vcpu->arch.pause) {
                if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1)
                        return PSCI_RET_ALREADY_ON;
                else
                        return PSCI_RET_INVALID_PARAMS;
        }

        target_pc = *vcpu_reg(source_vcpu, 2);
        context_id = *vcpu_reg(source_vcpu, 3);

        kvm_reset_vcpu(vcpu);

        /* Gracefully handle Thumb2 entry point */
        if (vcpu_mode_is_32bit(vcpu) && (target_pc & 1)) {
                target_pc &= ~((phys_addr_t) 1);
                vcpu_set_thumb(vcpu);
        }

        /* Propagate caller endianness */
        if (kvm_vcpu_is_be(source_vcpu))
                kvm_vcpu_set_be(vcpu);

        *vcpu_pc(vcpu) = target_pc;
        /*
         * NOTE: We always update r0 (or x0) because for PSCI v0.1
         * the general puspose registers are undefined upon CPU_ON.
         */
        *vcpu_reg(vcpu, 0) = context_id;
        vcpu->arch.pause = false;
        smp_mb();               /* Make sure the above is visible */

        wq = kvm_arch_vcpu_wq(vcpu);
        wake_up_interruptible(wq);

        return PSCI_RET_SUCCESS;
}

static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
{
        int i;
        unsigned long mpidr;
        unsigned long target_affinity;
        unsigned long target_affinity_mask;
        unsigned long lowest_affinity_level;
        struct kvm *kvm = vcpu->kvm;
        struct kvm_vcpu *tmp;

        target_affinity = *vcpu_reg(vcpu, 1);
        lowest_affinity_level = *vcpu_reg(vcpu, 2);

        /* Determine target affinity mask */
        target_affinity_mask = psci_affinity_mask(lowest_affinity_level);
        if (!target_affinity_mask)
                return PSCI_RET_INVALID_PARAMS;

        /* Ignore other bits of target affinity */
        target_affinity &= target_affinity_mask;

        /*
         * If one or more VCPU matching target affinity are running
         * then ON else OFF
         */
        kvm_for_each_vcpu(i, tmp, kvm) {
                mpidr = kvm_vcpu_get_mpidr(tmp);
                if (((mpidr & target_affinity_mask) == target_affinity) &&
                    !tmp->arch.pause) {
                        return PSCI_0_2_AFFINITY_LEVEL_ON;
                }
        }

        return PSCI_0_2_AFFINITY_LEVEL_OFF;
}

static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
{
        int i;
        struct kvm_vcpu *tmp;

        /*
         * The KVM ABI specifies that a system event exit may call KVM_RUN
         * again and may perform shutdown/reboot at a later time that when the
         * actual request is made.  Since we are implementing PSCI and a
         * caller of PSCI reboot and shutdown expects that the system shuts
         * down or reboots immediately, let's make sure that VCPUs are not run
         * after this call is handled and before the VCPUs have been
         * re-initialized.
         */
        kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
                tmp->arch.pause = true;
                kvm_vcpu_kick(tmp);
        }

        memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
        vcpu->run->system_event.type = type;
        vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
}

static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
{
        kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
}

static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
{
        kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
}

int kvm_psci_version(struct kvm_vcpu *vcpu)
{
        if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
                return KVM_ARM_PSCI_0_2;

        return KVM_ARM_PSCI_0_1;
}

static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
{
        int ret = 1;
        unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
        unsigned long val;

        switch (psci_fn) {
        case PSCI_0_2_FN_PSCI_VERSION:
                /*
                 * Bits[31:16] = Major Version = 0
                 * Bits[15:0] = Minor Version = 2
                 */
                val = 2;
                break;
        case PSCI_0_2_FN_CPU_SUSPEND:
        case PSCI_0_2_FN64_CPU_SUSPEND:
                val = kvm_psci_vcpu_suspend(vcpu);
                break;
        case PSCI_0_2_FN_CPU_OFF:
                kvm_psci_vcpu_off(vcpu);
                val = PSCI_RET_SUCCESS;
                break;
        case PSCI_0_2_FN_CPU_ON:
        case PSCI_0_2_FN64_CPU_ON:
                val = kvm_psci_vcpu_on(vcpu);
                break;
        case PSCI_0_2_FN_AFFINITY_INFO:
        case PSCI_0_2_FN64_AFFINITY_INFO:
                val = kvm_psci_vcpu_affinity_info(vcpu);
                break;
        case PSCI_0_2_FN_MIGRATE:
        case PSCI_0_2_FN64_MIGRATE:
                val = PSCI_RET_NOT_SUPPORTED;
                break;
        case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
                /*
                 * Trusted OS is MP hence does not require migration
                 * or
                 * Trusted OS is not present
                 */
                val = PSCI_0_2_TOS_MP;
                break;
        case PSCI_0_2_FN_MIGRATE_INFO_UP_CPU:
        case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU:
                val = PSCI_RET_NOT_SUPPORTED;
                break;
        case PSCI_0_2_FN_SYSTEM_OFF:
                kvm_psci_system_off(vcpu);
                /*
                 * We should'nt be going back to guest VCPU after
                 * receiving SYSTEM_OFF request.
                 *
                 * If user space accidently/deliberately resumes
                 * guest VCPU after SYSTEM_OFF request then guest
                 * VCPU should see internal failure from PSCI return
                 * value. To achieve this, we preload r0 (or x0) with
                 * PSCI return value INTERNAL_FAILURE.
                 */
                val = PSCI_RET_INTERNAL_FAILURE;
                ret = 0;
                break;
        case PSCI_0_2_FN_SYSTEM_RESET:
                kvm_psci_system_reset(vcpu);
                /*
                 * Same reason as SYSTEM_OFF for preloading r0 (or x0)
                 * with PSCI return value INTERNAL_FAILURE.
                 */
                val = PSCI_RET_INTERNAL_FAILURE;
                ret = 0;
                break;
        default:
                return -EINVAL;
        }

        *vcpu_reg(vcpu, 0) = val;
        return ret;
}

static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
{
        unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
        unsigned long val;

        switch (psci_fn) {
        case KVM_PSCI_FN_CPU_OFF:
                kvm_psci_vcpu_off(vcpu);
                val = PSCI_RET_SUCCESS;
                break;
        case KVM_PSCI_FN_CPU_ON:
                val = kvm_psci_vcpu_on(vcpu);
                break;
        case KVM_PSCI_FN_CPU_SUSPEND:
        case KVM_PSCI_FN_MIGRATE:
                val = PSCI_RET_NOT_SUPPORTED;
                break;
        default:
                return -EINVAL;
        }

        *vcpu_reg(vcpu, 0) = val;
        return 1;
}

/**
 * kvm_psci_call - handle PSCI call if r0 value is in range
 * @vcpu: Pointer to the VCPU struct
 *
 * Handle PSCI calls from guests through traps from HVC instructions.
 * The calling convention is similar to SMC calls to the secure world
 * where the function number is placed in r0.
 *
 * This function returns: > 0 (success), 0 (success but exit to user
 * space), and < 0 (errors)
 *
 * Errors:
 * -EINVAL: Unrecognized PSCI function
 */
int kvm_psci_call(struct kvm_vcpu *vcpu)
{
        switch (kvm_psci_version(vcpu)) {
        case KVM_ARM_PSCI_0_2:
                return kvm_psci_0_2_call(vcpu);
        case KVM_ARM_PSCI_0_1:
                return kvm_psci_0_1_call(vcpu);
        default:
                return -EINVAL;
        };
}