psci.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 - ARM Ltd
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 */
 
#include <linux/arm-smccc.h>
#include <linux/preempt.h>
#include <linux/kvm_host.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
 
#include <asm/cputype.h>
#include <asm/kvm_emulate.h>
 
#include <kvm/arm_psci.h>
#include <kvm/arm_hypercalls.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_wfi(vcpu);
 
    return PSCI_RET_SUCCESS;
}
 
static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu,
                       unsigned long affinity)
{
    return !(affinity & ~MPIDR_HWID_BITMASK);
}
 
static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
{
    struct vcpu_reset_state *reset_state;
    struct kvm *kvm = source_vcpu->kvm;
    struct kvm_vcpu *vcpu = NULL;
    int ret = PSCI_RET_SUCCESS;
    unsigned long cpu_id;
 
    cpu_id = smccc_get_arg1(source_vcpu);
    if (!kvm_psci_valid_affinity(source_vcpu, cpu_id))
        return PSCI_RET_INVALID_PARAMS;
 
    vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
 
    /*
     * Make sure the caller requested a valid CPU and that the CPU is
     * turned off.
     */
    if (!vcpu)
        return PSCI_RET_INVALID_PARAMS;
 
    spin_lock(&vcpu->arch.mp_state_lock);
    if (!kvm_arm_vcpu_stopped(vcpu)) {
        if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1)
            ret = PSCI_RET_ALREADY_ON;
        else
            ret = PSCI_RET_INVALID_PARAMS;
 
        goto out_unlock;
    }
 
    reset_state = &vcpu->arch.reset_state;
 
    reset_state->pc = smccc_get_arg2(source_vcpu);
 
    /* Propagate caller endianness */
    reset_state->be = kvm_vcpu_is_be(source_vcpu);
 
    /*
     * NOTE: We always update r0 (or x0) because for PSCI v0.1
     * the general purpose registers are undefined upon CPU_ON.
     */
    reset_state->r0 = smccc_get_arg3(source_vcpu);
 
    reset_state->reset = true;
    kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
 
    /*
     * Make sure the reset request is observed if the RUNNABLE mp_state is
     * observed.
     */
    smp_wmb();
 
    WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_RUNNABLE);
    kvm_vcpu_wake_up(vcpu);
 
out_unlock:
    spin_unlock(&vcpu->arch.mp_state_lock);
    return ret;
}
 
static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
{
    int matching_cpus = 0;
    unsigned long i, 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 = smccc_get_arg1(vcpu);
    lowest_affinity_level = smccc_get_arg2(vcpu);
 
    if (!kvm_psci_valid_affinity(vcpu, target_affinity))
        return PSCI_RET_INVALID_PARAMS;
 
    /* 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_aff(tmp);
        if ((mpidr & target_affinity_mask) == target_affinity) {
            matching_cpus++;
            if (!kvm_arm_vcpu_stopped(tmp))
                return PSCI_0_2_AFFINITY_LEVEL_ON;
        }
    }
 
    if (!matching_cpus)
        return PSCI_RET_INVALID_PARAMS;
 
    return PSCI_0_2_AFFINITY_LEVEL_OFF;
}
 
static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type, u64 flags)
{
    unsigned long 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) {
        spin_lock(&tmp->arch.mp_state_lock);
        WRITE_ONCE(tmp->arch.mp_state.mp_state, KVM_MP_STATE_STOPPED);
        spin_unlock(&tmp->arch.mp_state_lock);
    }
    kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
 
    memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
    vcpu->run->system_event.type = type;
    vcpu->run->system_event.ndata = 1;
    vcpu->run->system_event.data[0] = flags;
    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, 0);
}
 
static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
{
    kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET, 0);
}
 
static void kvm_psci_system_reset2(struct kvm_vcpu *vcpu)
{
    kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET,
                 KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2);
}
 
static void kvm_psci_system_suspend(struct kvm_vcpu *vcpu)
{
    struct kvm_run *run = vcpu->run;
 
    memset(&run->system_event, 0, sizeof(vcpu->run->system_event));
    run->system_event.type = KVM_SYSTEM_EVENT_SUSPEND;
    run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
}
 
static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu)
{
    int i;
 
    /*
     * Zero the input registers' upper 32 bits. They will be fully
     * zeroed on exit, so we're fine changing them in place.
     */
    for (i = 1; i < 4; i++)
        vcpu_set_reg(vcpu, i, lower_32_bits(vcpu_get_reg(vcpu, i)));
}
 
static unsigned long kvm_psci_check_allowed_function(struct kvm_vcpu *vcpu, u32 fn)
{
    /*
     * Prevent 32 bit guests from calling 64 bit PSCI functions.
     */
    if ((fn & PSCI_0_2_64BIT) && vcpu_mode_is_32bit(vcpu))
        return PSCI_RET_NOT_SUPPORTED;
 
    return 0;
}
 
static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
{
    u32 psci_fn = smccc_get_function(vcpu);
    unsigned long val;
    int ret = 1;
 
    switch (psci_fn) {
    case PSCI_0_2_FN_PSCI_VERSION:
        /*
         * Bits[31:16] = Major Version = 0
         * Bits[15:0] = Minor Version = 2
         */
        val = KVM_ARM_PSCI_0_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_arm_vcpu_power_off(vcpu);
        val = PSCI_RET_SUCCESS;
        break;
    case PSCI_0_2_FN_CPU_ON:
        kvm_psci_narrow_to_32bit(vcpu);
        fallthrough;
    case PSCI_0_2_FN64_CPU_ON:
        val = kvm_psci_vcpu_on(vcpu);
        break;
    case PSCI_0_2_FN_AFFINITY_INFO:
        kvm_psci_narrow_to_32bit(vcpu);
        fallthrough;
    case PSCI_0_2_FN64_AFFINITY_INFO:
        val = kvm_psci_vcpu_affinity_info(vcpu);
        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_SYSTEM_OFF:
        kvm_psci_system_off(vcpu);
        /*
         * We shouldn't be going back to guest VCPU after
         * receiving SYSTEM_OFF request.
         *
         * If user space accidentally/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:
        val = PSCI_RET_NOT_SUPPORTED;
        break;
    }
 
    smccc_set_retval(vcpu, val, 0, 0, 0);
    return ret;
}
 
static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
{
    unsigned long val = PSCI_RET_NOT_SUPPORTED;
    u32 psci_fn = smccc_get_function(vcpu);
    struct kvm *kvm = vcpu->kvm;
    u32 arg;
    int ret = 1;
 
    switch(psci_fn) {
    case PSCI_0_2_FN_PSCI_VERSION:
        val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
        break;
    case PSCI_1_0_FN_PSCI_FEATURES:
        arg = smccc_get_arg1(vcpu);
        val = kvm_psci_check_allowed_function(vcpu, arg);
        if (val)
            break;
 
        val = PSCI_RET_NOT_SUPPORTED;
 
        switch(arg) {
        case PSCI_0_2_FN_PSCI_VERSION:
        case PSCI_0_2_FN_CPU_SUSPEND:
        case PSCI_0_2_FN64_CPU_SUSPEND:
        case PSCI_0_2_FN_CPU_OFF:
        case PSCI_0_2_FN_CPU_ON:
        case PSCI_0_2_FN64_CPU_ON:
        case PSCI_0_2_FN_AFFINITY_INFO:
        case PSCI_0_2_FN64_AFFINITY_INFO:
        case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
        case PSCI_0_2_FN_SYSTEM_OFF:
        case PSCI_0_2_FN_SYSTEM_RESET:
        case PSCI_1_0_FN_PSCI_FEATURES:
        case ARM_SMCCC_VERSION_FUNC_ID:
            val = 0;
            break;
        case PSCI_1_0_FN_SYSTEM_SUSPEND:
        case PSCI_1_0_FN64_SYSTEM_SUSPEND:
            if (test_bit(KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED, &kvm->arch.flags))
                val = 0;
            break;
        case PSCI_1_1_FN_SYSTEM_RESET2:
        case PSCI_1_1_FN64_SYSTEM_RESET2:
            if (minor >= 1)
                val = 0;
            break;
        }
        break;
    case PSCI_1_0_FN_SYSTEM_SUSPEND:
        kvm_psci_narrow_to_32bit(vcpu);
        fallthrough;
    case PSCI_1_0_FN64_SYSTEM_SUSPEND:
        /*
         * Return directly to userspace without changing the vCPU's
         * registers. Userspace depends on reading the SMCCC parameters
         * to implement SYSTEM_SUSPEND.
         */
        if (test_bit(KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED, &kvm->arch.flags)) {
            kvm_psci_system_suspend(vcpu);
            return 0;
        }
        break;
    case PSCI_1_1_FN_SYSTEM_RESET2:
        kvm_psci_narrow_to_32bit(vcpu);
        fallthrough;
    case PSCI_1_1_FN64_SYSTEM_RESET2:
        if (minor >= 1) {
            arg = smccc_get_arg1(vcpu);
 
            if (arg <= PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET ||
                arg >= PSCI_1_1_RESET_TYPE_VENDOR_START) {
                kvm_psci_system_reset2(vcpu);
                vcpu_set_reg(vcpu, 0, PSCI_RET_INTERNAL_FAILURE);
                return 0;
            }
 
            val = PSCI_RET_INVALID_PARAMS;
            break;
        }
        break;
    default:
        return kvm_psci_0_2_call(vcpu);
    }
 
    smccc_set_retval(vcpu, val, 0, 0, 0);
    return ret;
}
 
static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
{
    u32 psci_fn = smccc_get_function(vcpu);
    unsigned long val;
 
    switch (psci_fn) {
    case KVM_PSCI_FN_CPU_OFF:
        kvm_arm_vcpu_power_off(vcpu);
        val = PSCI_RET_SUCCESS;
        break;
    case KVM_PSCI_FN_CPU_ON:
        val = kvm_psci_vcpu_on(vcpu);
        break;
    default:
        val = PSCI_RET_NOT_SUPPORTED;
        break;
    }
 
    smccc_set_retval(vcpu, val, 0, 0, 0);
    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)
{
    u32 psci_fn = smccc_get_function(vcpu);
    int version = kvm_psci_version(vcpu);
    unsigned long val;
 
    val = kvm_psci_check_allowed_function(vcpu, psci_fn);
    if (val) {
        smccc_set_retval(vcpu, val, 0, 0, 0);
        return 1;
    }
 
    switch (version) {
    case KVM_ARM_PSCI_1_1:
        return kvm_psci_1_x_call(vcpu, 1);
    case KVM_ARM_PSCI_1_0:
        return kvm_psci_1_x_call(vcpu, 0);
    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:
        WARN_ONCE(1, "Unknown PSCI version %d", version);
        smccc_set_retval(vcpu, SMCCC_RET_NOT_SUPPORTED, 0, 0, 0);
        return 1;
    }
}