psci-relay.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 - Google LLC
 * Author: David Brazdil <dbrazdil@google.com>
 */
 
#include <asm/kvm_asm.h>
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
#include <linux/arm-smccc.h>
#include <linux/kvm_host.h>
#include <uapi/linux/psci.h>
 
#include <nvhe/memory.h>
#include <nvhe/trap_handler.h>
 
void kvm_hyp_cpu_entry(unsigned long r0);
void kvm_hyp_cpu_resume(unsigned long r0);
 
void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
 
/* Config options set by the host. */
struct kvm_host_psci_config __ro_after_init kvm_host_psci_config;
 
#define INVALID_CPU_ID  UINT_MAX
 
struct psci_boot_args {
    atomic_t lock;
    unsigned long pc;
    unsigned long r0;
};
 
#define PSCI_BOOT_ARGS_UNLOCKED     0
#define PSCI_BOOT_ARGS_LOCKED       1
 
#define PSCI_BOOT_ARGS_INIT                 \
    ((struct psci_boot_args){               \
        .lock = ATOMIC_INIT(PSCI_BOOT_ARGS_UNLOCKED),   \
    })
 
static DEFINE_PER_CPU(struct psci_boot_args, cpu_on_args) = PSCI_BOOT_ARGS_INIT;
static DEFINE_PER_CPU(struct psci_boot_args, suspend_args) = PSCI_BOOT_ARGS_INIT;
 
#define is_psci_0_1(what, func_id)                  \
    (kvm_host_psci_config.psci_0_1_ ## what ## _implemented &&  \
     (func_id) == kvm_host_psci_config.function_ids_0_1.what)
 
static bool is_psci_0_1_call(u64 func_id)
{
    return (is_psci_0_1(cpu_suspend, func_id) ||
        is_psci_0_1(cpu_on, func_id) ||
        is_psci_0_1(cpu_off, func_id) ||
        is_psci_0_1(migrate, func_id));
}
 
static bool is_psci_0_2_call(u64 func_id)
{
    /* SMCCC reserves IDs 0x00-1F with the given 32/64-bit base for PSCI. */
    return (PSCI_0_2_FN(0) <= func_id && func_id <= PSCI_0_2_FN(31)) ||
           (PSCI_0_2_FN64(0) <= func_id && func_id <= PSCI_0_2_FN64(31));
}
 
static unsigned long psci_call(unsigned long fn, unsigned long arg0,
                   unsigned long arg1, unsigned long arg2)
{
    struct arm_smccc_res res;
 
    arm_smccc_1_1_smc(fn, arg0, arg1, arg2, &res);
    return res.a0;
}
 
static unsigned long psci_forward(struct kvm_cpu_context *host_ctxt)
{
    return psci_call(cpu_reg(host_ctxt, 0), cpu_reg(host_ctxt, 1),
             cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3));
}
 
static unsigned int find_cpu_id(u64 mpidr)
{
    unsigned int i;
 
    /* Reject invalid MPIDRs */
    if (mpidr & ~MPIDR_HWID_BITMASK)
        return INVALID_CPU_ID;
 
    for (i = 0; i < NR_CPUS; i++) {
        if (cpu_logical_map(i) == mpidr)
            return i;
    }
 
    return INVALID_CPU_ID;
}
 
static __always_inline bool try_acquire_boot_args(struct psci_boot_args *args)
{
    return atomic_cmpxchg_acquire(&args->lock,
                      PSCI_BOOT_ARGS_UNLOCKED,
                      PSCI_BOOT_ARGS_LOCKED) ==
        PSCI_BOOT_ARGS_UNLOCKED;
}
 
static __always_inline void release_boot_args(struct psci_boot_args *args)
{
    atomic_set_release(&args->lock, PSCI_BOOT_ARGS_UNLOCKED);
}
 
static int psci_cpu_on(u64 func_id, struct kvm_cpu_context *host_ctxt)
{
    DECLARE_REG(u64, mpidr, host_ctxt, 1);
    DECLARE_REG(unsigned long, pc, host_ctxt, 2);
    DECLARE_REG(unsigned long, r0, host_ctxt, 3);
 
    unsigned int cpu_id;
    struct psci_boot_args *boot_args;
    struct kvm_nvhe_init_params *init_params;
    int ret;
 
    /*
     * Find the logical CPU ID for the given MPIDR. The search set is
     * the set of CPUs that were online at the point of KVM initialization.
     * Booting other CPUs is rejected because their cpufeatures were not
     * checked against the finalized capabilities. This could be relaxed
     * by doing the feature checks in hyp.
     */
    cpu_id = find_cpu_id(mpidr);
    if (cpu_id == INVALID_CPU_ID)
        return PSCI_RET_INVALID_PARAMS;
 
    boot_args = per_cpu_ptr(&cpu_on_args, cpu_id);
    init_params = per_cpu_ptr(&kvm_init_params, cpu_id);
 
    /* Check if the target CPU is already being booted. */
    if (!try_acquire_boot_args(boot_args))
        return PSCI_RET_ALREADY_ON;
 
    boot_args->pc = pc;
    boot_args->r0 = r0;
    wmb();
 
    ret = psci_call(func_id, mpidr,
            __hyp_pa(&kvm_hyp_cpu_entry),
            __hyp_pa(init_params));
 
    /* If successful, the lock will be released by the target CPU. */
    if (ret != PSCI_RET_SUCCESS)
        release_boot_args(boot_args);
 
    return ret;
}
 
static int psci_cpu_suspend(u64 func_id, struct kvm_cpu_context *host_ctxt)
{
    DECLARE_REG(u64, power_state, host_ctxt, 1);
    DECLARE_REG(unsigned long, pc, host_ctxt, 2);
    DECLARE_REG(unsigned long, r0, host_ctxt, 3);
 
    struct psci_boot_args *boot_args;
    struct kvm_nvhe_init_params *init_params;
 
    boot_args = this_cpu_ptr(&suspend_args);
    init_params = this_cpu_ptr(&kvm_init_params);
 
    /*
     * No need to acquire a lock before writing to boot_args because a core
     * can only suspend itself. Racy CPU_ON calls use a separate struct.
     */
    boot_args->pc = pc;
    boot_args->r0 = r0;
 
    /*
     * Will either return if shallow sleep state, or wake up into the entry
     * point if it is a deep sleep state.
     */
    return psci_call(func_id, power_state,
             __hyp_pa(&kvm_hyp_cpu_resume),
             __hyp_pa(init_params));
}
 
static int psci_system_suspend(u64 func_id, struct kvm_cpu_context *host_ctxt)
{
    DECLARE_REG(unsigned long, pc, host_ctxt, 1);
    DECLARE_REG(unsigned long, r0, host_ctxt, 2);
 
    struct psci_boot_args *boot_args;
    struct kvm_nvhe_init_params *init_params;
 
    boot_args = this_cpu_ptr(&suspend_args);
    init_params = this_cpu_ptr(&kvm_init_params);
 
    /*
     * No need to acquire a lock before writing to boot_args because a core
     * can only suspend itself. Racy CPU_ON calls use a separate struct.
     */
    boot_args->pc = pc;
    boot_args->r0 = r0;
 
    /* Will only return on error. */
    return psci_call(func_id,
             __hyp_pa(&kvm_hyp_cpu_resume),
             __hyp_pa(init_params), 0);
}
 
asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
{
    struct psci_boot_args *boot_args;
    struct kvm_cpu_context *host_ctxt;
 
    host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
 
    if (is_cpu_on)
        boot_args = this_cpu_ptr(&cpu_on_args);
    else
        boot_args = this_cpu_ptr(&suspend_args);
 
    cpu_reg(host_ctxt, 0) = boot_args->r0;
    write_sysreg_el2(boot_args->pc, SYS_ELR);
 
    if (is_cpu_on)
        release_boot_args(boot_args);
 
    __host_enter(host_ctxt);
}
 
static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
{
    if (is_psci_0_1(cpu_off, func_id) || is_psci_0_1(migrate, func_id))
        return psci_forward(host_ctxt);
    if (is_psci_0_1(cpu_on, func_id))
        return psci_cpu_on(func_id, host_ctxt);
    if (is_psci_0_1(cpu_suspend, func_id))
        return psci_cpu_suspend(func_id, host_ctxt);
 
    return PSCI_RET_NOT_SUPPORTED;
}
 
static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
{
    switch (func_id) {
    case PSCI_0_2_FN_PSCI_VERSION:
    case PSCI_0_2_FN_CPU_OFF:
    case PSCI_0_2_FN64_AFFINITY_INFO:
    case PSCI_0_2_FN64_MIGRATE:
    case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
    case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU:
        return psci_forward(host_ctxt);
    /*
     * SYSTEM_OFF/RESET should not return according to the spec.
     * Allow it so as to stay robust to broken firmware.
     */
    case PSCI_0_2_FN_SYSTEM_OFF:
    case PSCI_0_2_FN_SYSTEM_RESET:
        return psci_forward(host_ctxt);
    case PSCI_0_2_FN64_CPU_SUSPEND:
        return psci_cpu_suspend(func_id, host_ctxt);
    case PSCI_0_2_FN64_CPU_ON:
        return psci_cpu_on(func_id, host_ctxt);
    default:
        return PSCI_RET_NOT_SUPPORTED;
    }
}
 
static unsigned long psci_1_0_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
{
    switch (func_id) {
    case PSCI_1_0_FN_PSCI_FEATURES:
    case PSCI_1_0_FN_SET_SUSPEND_MODE:
    case PSCI_1_1_FN64_SYSTEM_RESET2:
        return psci_forward(host_ctxt);
    case PSCI_1_0_FN64_SYSTEM_SUSPEND:
        return psci_system_suspend(func_id, host_ctxt);
    default:
        return psci_0_2_handler(func_id, host_ctxt);
    }
}
 
bool kvm_host_psci_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
{
    unsigned long ret;
 
    switch (kvm_host_psci_config.version) {
    case PSCI_VERSION(0, 1):
        if (!is_psci_0_1_call(func_id))
            return false;
        ret = psci_0_1_handler(func_id, host_ctxt);
        break;
    case PSCI_VERSION(0, 2):
        if (!is_psci_0_2_call(func_id))
            return false;
        ret = psci_0_2_handler(func_id, host_ctxt);
        break;
    default:
        if (!is_psci_0_2_call(func_id))
            return false;
        ret = psci_1_0_handler(func_id, host_ctxt);
        break;
    }
 
    cpu_reg(host_ctxt, 0) = ret;
    cpu_reg(host_ctxt, 1) = 0;
    cpu_reg(host_ctxt, 2) = 0;
    cpu_reg(host_ctxt, 3) = 0;
    return true;
}