cpu_helper.c

/*
 * RISC-V CPU helpers for qemu.
 *
 * Copyright (c) 2016-2017 Sagar Karandikar, sagark@eecs.berkeley.edu
 * Copyright (c) 2017-2018 SiFive, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2 or later, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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 "qemu/osdep.h"
#include "qemu/log.h"
#include "cpu.h"
#include "exec/exec-all.h"
#include "tcg-op.h"
#include "trace.h"

int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch)
{
#ifdef CONFIG_USER_ONLY
    return 0;
#else
    return env->priv;
#endif
}

#ifndef CONFIG_USER_ONLY
static int riscv_cpu_local_irq_pending(CPURISCVState *env)
{
    target_ulong mstatus_mie = get_field(env->mstatus, MSTATUS_MIE);
    target_ulong mstatus_sie = get_field(env->mstatus, MSTATUS_SIE);
    target_ulong pending = atomic_read(&env->mip) & env->mie;
    target_ulong mie = env->priv < PRV_M || (env->priv == PRV_M && mstatus_mie);
    target_ulong sie = env->priv < PRV_S || (env->priv == PRV_S && mstatus_sie);
    target_ulong irqs = (pending & ~env->mideleg & -mie) |
                        (pending &  env->mideleg & -sie);

    if (irqs) {
        return ctz64(irqs); /* since non-zero */
    } else {
        return EXCP_NONE; /* indicates no pending interrupt */
    }
}
#endif

bool riscv_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
{
#if !defined(CONFIG_USER_ONLY)
    if (interrupt_request & CPU_INTERRUPT_HARD) {
        RISCVCPU *cpu = RISCV_CPU(cs);
        CPURISCVState *env = &cpu->env;
        int interruptno = riscv_cpu_local_irq_pending(env);
        if (interruptno >= 0) {
            cs->exception_index = RISCV_EXCP_INT_FLAG | interruptno;
            riscv_cpu_do_interrupt(cs);
            return true;
        }
    }
#endif
    return false;
}

#if !defined(CONFIG_USER_ONLY)

int riscv_cpu_claim_interrupts(RISCVCPU *cpu, uint32_t interrupts)
{
    CPURISCVState *env = &cpu->env;
    if (env->miclaim & interrupts) {
        return -1;
    } else {
        env->miclaim |= interrupts;
        return 0;
    }
}

struct CpuAsyncInfo {
    uint32_t new_mip;
};

static void riscv_cpu_update_mip_irqs_async(CPUState *target_cpu_state,
                                            run_on_cpu_data data)
{
    struct CpuAsyncInfo *info = (struct CpuAsyncInfo *) data.host_ptr;

    if (info->new_mip) {
        cpu_interrupt(target_cpu_state, CPU_INTERRUPT_HARD);
    } else {
        cpu_reset_interrupt(target_cpu_state, CPU_INTERRUPT_HARD);
    }

    g_free(info);
}

uint32_t riscv_cpu_update_mip(RISCVCPU *cpu, uint32_t mask, uint32_t value)
{
    CPURISCVState *env = &cpu->env;
    CPUState *cs = CPU(cpu);
    struct CpuAsyncInfo *info;
    uint32_t old, new, cmp = atomic_read(&env->mip);

    do {
        old = cmp;
        new = (old & ~mask) | (value & mask);
        cmp = atomic_cmpxchg(&env->mip, old, new);
    } while (old != cmp);

    info = g_new(struct CpuAsyncInfo, 1);
    info->new_mip = new;

    async_run_on_cpu(cs, riscv_cpu_update_mip_irqs_async,
                     RUN_ON_CPU_HOST_PTR(info));

    return old;
}

void riscv_cpu_set_mode(CPURISCVState *env, target_ulong newpriv)
{
    if (newpriv > PRV_M) {
        g_assert_not_reached();
    }
    if (newpriv == PRV_H) {
        newpriv = PRV_U;
    }
    /* tlb_flush is unnecessary as mode is contained in mmu_idx */
    env->priv = newpriv;
}

/* get_physical_address - get the physical address for this virtual address
 *
 * Do a page table walk to obtain the physical address corresponding to a
 * virtual address. Returns 0 if the translation was successful
 *
 * Adapted from Spike's mmu_t::translate and mmu_t::walk
 *
 */
static int get_physical_address(CPURISCVState *env, hwaddr *physical,
                                int *prot, target_ulong addr,
                                int access_type, int mmu_idx)
{
    /* NOTE: the env->pc value visible here will not be
     * correct, but the value visible to the exception handler
     * (riscv_cpu_do_interrupt) is correct */

    int mode = mmu_idx;

    if (mode == PRV_M && access_type != MMU_INST_FETCH) {
        if (get_field(env->mstatus, MSTATUS_MPRV)) {
            mode = get_field(env->mstatus, MSTATUS_MPP);
        }
    }

    if (mode == PRV_M || !riscv_feature(env, RISCV_FEATURE_MMU)) {
        *physical = addr;
        *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
        return TRANSLATE_SUCCESS;
    }

    *prot = 0;

    target_ulong base;
    int levels, ptidxbits, ptesize, vm, sum;
    int mxr = get_field(env->mstatus, MSTATUS_MXR);

    if (env->priv_ver >= PRIV_VERSION_1_10_0) {
        base = get_field(env->satp, SATP_PPN) << PGSHIFT;
        sum = get_field(env->mstatus, MSTATUS_SUM);
        vm = get_field(env->satp, SATP_MODE);
        switch (vm) {
        case VM_1_10_SV32:
          levels = 2; ptidxbits = 10; ptesize = 4; break;
        case VM_1_10_SV39:
          levels = 3; ptidxbits = 9; ptesize = 8; break;
        case VM_1_10_SV48:
          levels = 4; ptidxbits = 9; ptesize = 8; break;
        case VM_1_10_SV57:
          levels = 5; ptidxbits = 9; ptesize = 8; break;
        case VM_1_10_MBARE:
            *physical = addr;
            *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
            return TRANSLATE_SUCCESS;
        default:
          g_assert_not_reached();
        }
    } else {
        base = env->sptbr << PGSHIFT;
        sum = !get_field(env->mstatus, MSTATUS_PUM);
        vm = get_field(env->mstatus, MSTATUS_VM);
        switch (vm) {
        case VM_1_09_SV32:
          levels = 2; ptidxbits = 10; ptesize = 4; break;
        case VM_1_09_SV39:
          levels = 3; ptidxbits = 9; ptesize = 8; break;
        case VM_1_09_SV48:
          levels = 4; ptidxbits = 9; ptesize = 8; break;
        case VM_1_09_MBARE:
            *physical = addr;
            *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
            return TRANSLATE_SUCCESS;
        default:
          g_assert_not_reached();
        }
    }

    CPUState *cs = env_cpu(env);
    int va_bits = PGSHIFT + levels * ptidxbits;
    target_ulong mask = (1L << (TARGET_LONG_BITS - (va_bits - 1))) - 1;
    target_ulong masked_msbs = (addr >> (va_bits - 1)) & mask;
    if (masked_msbs != 0 && masked_msbs != mask) {
        return TRANSLATE_FAIL;
    }

    int ptshift = (levels - 1) * ptidxbits;
    int i;

#if !TCG_OVERSIZED_GUEST
restart:
#endif
    for (i = 0; i < levels; i++, ptshift -= ptidxbits) {
        target_ulong idx = (addr >> (PGSHIFT + ptshift)) &
                           ((1 << ptidxbits) - 1);

        /* check that physical address of PTE is legal */
        target_ulong pte_addr = base + idx * ptesize;

        if (riscv_feature(env, RISCV_FEATURE_PMP) &&
            !pmp_hart_has_privs(env, pte_addr, sizeof(target_ulong),
            1 << MMU_DATA_LOAD, PRV_S)) {
            return TRANSLATE_PMP_FAIL;
        }
#if defined(TARGET_RISCV32)
        target_ulong pte = ldl_phys(cs->as, pte_addr);
#elif defined(TARGET_RISCV64)
        target_ulong pte = ldq_phys(cs->as, pte_addr);
#endif
        target_ulong ppn = pte >> PTE_PPN_SHIFT;

        if (!(pte & PTE_V)) {
            /* Invalid PTE */
            return TRANSLATE_FAIL;
        } else if (!(pte & (PTE_R | PTE_W | PTE_X))) {
            /* Inner PTE, continue walking */
            base = ppn << PGSHIFT;
        } else if ((pte & (PTE_R | PTE_W | PTE_X)) == PTE_W) {
            /* Reserved leaf PTE flags: PTE_W */
            return TRANSLATE_FAIL;
        } else if ((pte & (PTE_R | PTE_W | PTE_X)) == (PTE_W | PTE_X)) {
            /* Reserved leaf PTE flags: PTE_W + PTE_X */
            return TRANSLATE_FAIL;
        } else if ((pte & PTE_U) && ((mode != PRV_U) &&
                   (!sum || access_type == MMU_INST_FETCH))) {
            /* User PTE flags when not U mode and mstatus.SUM is not set,
               or the access type is an instruction fetch */
            return TRANSLATE_FAIL;
        } else if (!(pte & PTE_U) && (mode != PRV_S)) {
            /* Supervisor PTE flags when not S mode */
            return TRANSLATE_FAIL;
        } else if (ppn & ((1ULL << ptshift) - 1)) {
            /* Misaligned PPN */
            return TRANSLATE_FAIL;
        } else if (access_type == MMU_DATA_LOAD && !((pte & PTE_R) ||
                   ((pte & PTE_X) && mxr))) {
            /* Read access check failed */
            return TRANSLATE_FAIL;
        } else if (access_type == MMU_DATA_STORE && !(pte & PTE_W)) {
            /* Write access check failed */
            return TRANSLATE_FAIL;
        } else if (access_type == MMU_INST_FETCH && !(pte & PTE_X)) {
            /* Fetch access check failed */
            return TRANSLATE_FAIL;
        } else {
            /* if necessary, set accessed and dirty bits. */
            target_ulong updated_pte = pte | PTE_A |
                (access_type == MMU_DATA_STORE ? PTE_D : 0);

            /* Page table updates need to be atomic with MTTCG enabled */
            if (updated_pte != pte) {
                /*
                 * - if accessed or dirty bits need updating, and the PTE is
                 *   in RAM, then we do so atomically with a compare and swap.
                 * - if the PTE is in IO space or ROM, then it can't be updated
                 *   and we return TRANSLATE_FAIL.
                 * - if the PTE changed by the time we went to update it, then
                 *   it is no longer valid and we must re-walk the page table.
                 */
                MemoryRegion *mr;
                hwaddr l = sizeof(target_ulong), addr1;
                mr = address_space_translate(cs->as, pte_addr,
                    &addr1, &l, false, MEMTXATTRS_UNSPECIFIED);
                if (memory_region_is_ram(mr)) {
                    target_ulong *pte_pa =
                        qemu_map_ram_ptr(mr->ram_block, addr1);
#if TCG_OVERSIZED_GUEST
                    /* MTTCG is not enabled on oversized TCG guests so
                     * page table updates do not need to be atomic */
                    *pte_pa = pte = updated_pte;
#else
                    target_ulong old_pte =
                        atomic_cmpxchg(pte_pa, pte, updated_pte);
                    if (old_pte != pte) {
                        goto restart;
                    } else {
                        pte = updated_pte;
                    }
#endif
                } else {
                    /* misconfigured PTE in ROM (AD bits are not preset) or
                     * PTE is in IO space and can't be updated atomically */
                    return TRANSLATE_FAIL;
                }
            }

            /* for superpage mappings, make a fake leaf PTE for the TLB's
               benefit. */
            target_ulong vpn = addr >> PGSHIFT;
            *physical = (ppn | (vpn & ((1L << ptshift) - 1))) << PGSHIFT;

            /* set permissions on the TLB entry */
            if ((pte & PTE_R) || ((pte & PTE_X) && mxr)) {
                *prot |= PAGE_READ;
            }
            if ((pte & PTE_X)) {
                *prot |= PAGE_EXEC;
            }
            /* add write permission on stores or if the page is already dirty,
               so that we TLB miss on later writes to update the dirty bit */
            if ((pte & PTE_W) &&
                    (access_type == MMU_DATA_STORE || (pte & PTE_D))) {
                *prot |= PAGE_WRITE;
            }
            return TRANSLATE_SUCCESS;
        }
    }
    return TRANSLATE_FAIL;
}

static void raise_mmu_exception(CPURISCVState *env, target_ulong address,
                                MMUAccessType access_type, bool pmp_violation)
{
    CPUState *cs = env_cpu(env);
    int page_fault_exceptions =
        (env->priv_ver >= PRIV_VERSION_1_10_0) &&
        get_field(env->satp, SATP_MODE) != VM_1_10_MBARE &&
        !pmp_violation;
    switch (access_type) {
    case MMU_INST_FETCH:
        cs->exception_index = page_fault_exceptions ?
            RISCV_EXCP_INST_PAGE_FAULT : RISCV_EXCP_INST_ACCESS_FAULT;
        break;
    case MMU_DATA_LOAD:
        cs->exception_index = page_fault_exceptions ?
            RISCV_EXCP_LOAD_PAGE_FAULT : RISCV_EXCP_LOAD_ACCESS_FAULT;
        break;
    case MMU_DATA_STORE:
        cs->exception_index = page_fault_exceptions ?
            RISCV_EXCP_STORE_PAGE_FAULT : RISCV_EXCP_STORE_AMO_ACCESS_FAULT;
        break;
    default:
        g_assert_not_reached();
    }
    env->badaddr = address;
}

hwaddr riscv_cpu_get_phys_page_debug(CPUState *cs, vaddr addr)
{
    RISCVCPU *cpu = RISCV_CPU(cs);
    hwaddr phys_addr;
    int prot;
    int mmu_idx = cpu_mmu_index(&cpu->env, false);

    if (get_physical_address(&cpu->env, &phys_addr, &prot, addr, 0, mmu_idx)) {
        return -1;
    }
    return phys_addr;
}

void riscv_cpu_unassigned_access(CPUState *cs, hwaddr addr, bool is_write,
                                 bool is_exec, int unused, unsigned size)
{
    RISCVCPU *cpu = RISCV_CPU(cs);
    CPURISCVState *env = &cpu->env;

    if (is_write) {
        cs->exception_index = RISCV_EXCP_STORE_AMO_ACCESS_FAULT;
    } else {
        cs->exception_index = RISCV_EXCP_LOAD_ACCESS_FAULT;
    }

    env->badaddr = addr;
    riscv_raise_exception(&cpu->env, cs->exception_index, GETPC());
}

void riscv_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
                                   MMUAccessType access_type, int mmu_idx,
                                   uintptr_t retaddr)
{
    RISCVCPU *cpu = RISCV_CPU(cs);
    CPURISCVState *env = &cpu->env;
    switch (access_type) {
    case MMU_INST_FETCH:
        cs->exception_index = RISCV_EXCP_INST_ADDR_MIS;
        break;
    case MMU_DATA_LOAD:
        cs->exception_index = RISCV_EXCP_LOAD_ADDR_MIS;
        break;
    case MMU_DATA_STORE:
        cs->exception_index = RISCV_EXCP_STORE_AMO_ADDR_MIS;
        break;
    default:
        g_assert_not_reached();
    }
    env->badaddr = addr;
    riscv_raise_exception(env, cs->exception_index, retaddr);
}
#endif

bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
                        MMUAccessType access_type, int mmu_idx,
                        bool probe, uintptr_t retaddr)
{
#ifndef CONFIG_USER_ONLY
    RISCVCPU *cpu = RISCV_CPU(cs);
    CPURISCVState *env = &cpu->env;
    hwaddr pa = 0;
    int prot;
    bool pmp_violation = false;
    int ret = TRANSLATE_FAIL;
    int mode = mmu_idx;

    qemu_log_mask(CPU_LOG_MMU, "%s ad %" VADDR_PRIx " rw %d mmu_idx %d\n",
                  __func__, address, access_type, mmu_idx);

    ret = get_physical_address(env, &pa, &prot, address, access_type, mmu_idx);

    if (mode == PRV_M && access_type != MMU_INST_FETCH) {
        if (get_field(env->mstatus, MSTATUS_MPRV)) {
            mode = get_field(env->mstatus, MSTATUS_MPP);
        }
    }

    qemu_log_mask(CPU_LOG_MMU,
                  "%s address=%" VADDR_PRIx " ret %d physical " TARGET_FMT_plx
                  " prot %d\n", __func__, address, ret, pa, prot);

    if (riscv_feature(env, RISCV_FEATURE_PMP) &&
        (ret == TRANSLATE_SUCCESS) &&
        !pmp_hart_has_privs(env, pa, size, 1 << access_type, mode)) {
        ret = TRANSLATE_PMP_FAIL;
    }
    if (ret == TRANSLATE_PMP_FAIL) {
        pmp_violation = true;
    }
    if (ret == TRANSLATE_SUCCESS) {
        tlb_set_page(cs, address & TARGET_PAGE_MASK, pa & TARGET_PAGE_MASK,
                     prot, mmu_idx, TARGET_PAGE_SIZE);
        return true;
    } else if (probe) {
        return false;
    } else {
        raise_mmu_exception(env, address, access_type, pmp_violation);
        riscv_raise_exception(env, cs->exception_index, retaddr);
    }
#else
    switch (access_type) {
    case MMU_INST_FETCH:
        cs->exception_index = RISCV_EXCP_INST_PAGE_FAULT;
        break;
    case MMU_DATA_LOAD:
        cs->exception_index = RISCV_EXCP_LOAD_PAGE_FAULT;
        break;
    case MMU_DATA_STORE:
        cs->exception_index = RISCV_EXCP_STORE_PAGE_FAULT;
        break;
    }
    cpu_loop_exit_restore(cs, retaddr);
#endif
}

/*
 * Handle Traps
 *
 * Adapted from Spike's processor_t::take_trap.
 *
 */
void riscv_cpu_do_interrupt(CPUState *cs)
{
#if !defined(CONFIG_USER_ONLY)

    RISCVCPU *cpu = RISCV_CPU(cs);
    CPURISCVState *env = &cpu->env;

    /* cs->exception is 32-bits wide unlike mcause which is XLEN-bits wide
     * so we mask off the MSB and separate into trap type and cause.
     */
    bool async = !!(cs->exception_index & RISCV_EXCP_INT_FLAG);
    target_ulong cause = cs->exception_index & RISCV_EXCP_INT_MASK;
    target_ulong deleg = async ? env->mideleg : env->medeleg;
    target_ulong tval = 0;

    static const int ecall_cause_map[] = {
        [PRV_U] = RISCV_EXCP_U_ECALL,
        [PRV_S] = RISCV_EXCP_S_ECALL,
        [PRV_H] = RISCV_EXCP_H_ECALL,
        [PRV_M] = RISCV_EXCP_M_ECALL
    };

    if (!async) {
        /* set tval to badaddr for traps with address information */
        switch (cause) {
        case RISCV_EXCP_INST_ADDR_MIS:
        case RISCV_EXCP_INST_ACCESS_FAULT:
        case RISCV_EXCP_LOAD_ADDR_MIS:
        case RISCV_EXCP_STORE_AMO_ADDR_MIS:
        case RISCV_EXCP_LOAD_ACCESS_FAULT:
        case RISCV_EXCP_STORE_AMO_ACCESS_FAULT:
        case RISCV_EXCP_INST_PAGE_FAULT:
        case RISCV_EXCP_LOAD_PAGE_FAULT:
        case RISCV_EXCP_STORE_PAGE_FAULT:
            tval = env->badaddr;
            break;
        default:
            break;
        }
        /* ecall is dispatched as one cause so translate based on mode */
        if (cause == RISCV_EXCP_U_ECALL) {
            assert(env->priv <= 3);
            cause = ecall_cause_map[env->priv];
        }
    }

    trace_riscv_trap(env->mhartid, async, cause, env->pc, tval, cause < 16 ?
        (async ? riscv_intr_names : riscv_excp_names)[cause] : "(unknown)");

    if (env->priv <= PRV_S &&
            cause < TARGET_LONG_BITS && ((deleg >> cause) & 1)) {
        /* handle the trap in S-mode */
        target_ulong s = env->mstatus;
        s = set_field(s, MSTATUS_SPIE, env->priv_ver >= PRIV_VERSION_1_10_0 ?
            get_field(s, MSTATUS_SIE) : get_field(s, MSTATUS_UIE << env->priv));
        s = set_field(s, MSTATUS_SPP, env->priv);
        s = set_field(s, MSTATUS_SIE, 0);
        env->mstatus = s;
        env->scause = cause | ((target_ulong)async << (TARGET_LONG_BITS - 1));
        env->sepc = env->pc;
        env->sbadaddr = tval;
        env->pc = (env->stvec >> 2 << 2) +
            ((async && (env->stvec & 3) == 1) ? cause * 4 : 0);
        riscv_cpu_set_mode(env, PRV_S);
    } else {
        /* handle the trap in M-mode */
        target_ulong s = env->mstatus;
        s = set_field(s, MSTATUS_MPIE, env->priv_ver >= PRIV_VERSION_1_10_0 ?
            get_field(s, MSTATUS_MIE) : get_field(s, MSTATUS_UIE << env->priv));
        s = set_field(s, MSTATUS_MPP, env->priv);
        s = set_field(s, MSTATUS_MIE, 0);
        env->mstatus = s;
        env->mcause = cause | ~(((target_ulong)-1) >> async);
        env->mepc = env->pc;
        env->mbadaddr = tval;
        env->pc = (env->mtvec >> 2 << 2) +
            ((async && (env->mtvec & 3) == 1) ? cause * 4 : 0);
        riscv_cpu_set_mode(env, PRV_M);
    }

    /* NOTE: it is not necessary to yield load reservations here. It is only
     * necessary for an SC from "another hart" to cause a load reservation
     * to be yielded. Refer to the memory consistency model section of the
     * RISC-V ISA Specification.
     */

#endif
    cs->exception_index = EXCP_NONE; /* mark handled to qemu */
}