Re: [PATCH v4] riscv: Allow user to set the satp mode

[Frank Chang <frank.chang@sifive.com>]

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Hi Alexandre,

Thanks for the contribution. This is really helpful.

It seems like if we want to specify the SATP mode for the "named" CPUs,
we have to do, e.g.:
cpu->cfg.satp_mode.map |= (1 << idx_satp_mode_from_str("sv39"));
in each CPU's init function.

Can we add another helper function to wrap this for the "named" CPUs?

Regards,
Frank Chang


On Mon, Dec 12, 2022 at 6:23 PM Alexandre Ghiti <alexghiti@rivosinc.com>
wrote:

> RISC-V specifies multiple sizes for addressable memory and Linux probes for
> the machine's support at startup via the satp CSR register (done in
> csr.c:validate_vm).
>
> As per the specification, sv64 must support sv57, which in turn must
> support sv48...etc. So we can restrict machine support by simply setting
> the
> "highest" supported mode and the bare mode is always supported.
>
> You can set the satp mode using the new properties "mbare", "sv32",
> "sv39", "sv48", "sv57" and "sv64" as follows:
> -cpu rv64,sv57=on # Linux will boot using sv57 scheme
> -cpu rv64,sv39=on # Linux will boot using sv39 scheme
>
> We take the highest level set by the user:
> -cpu rv64,sv48=on,sv57=on # Linux will boot using sv57 scheme
>
> We make sure that invalid configurations are rejected:
> -cpu rv64,sv32=on # Can't enable 32-bit satp mode in 64-bit
> -cpu rv64,sv39=off,sv48=on # sv39 must be supported if higher modes are
>                            # enabled
>
> We accept "redundant" configurations:
> -cpu rv64,sv48=on,sv57=off # sv39 must be supported if higher modes are
>
> In addition, we now correctly set the device-tree entry 'mmu-type' using
> those new properties.
>
> Co-Developed-by: Ludovic Henry <ludovic@rivosinc.com>
> Signed-off-by: Ludovic Henry <ludovic@rivosinc.com>
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
> v4:
> - Use custom boolean properties instead of OnOffAuto properties, based
>   on ARMVQMap, as suggested by Andrew
>
> v3:
> - Free sv_name as pointed by Bin
> - Replace satp-mode with boolean properties as suggested by Andrew
> - Removed RB from Atish as the patch considerably changed
>
> v2:
> - Use error_setg + return as suggested by Alistair
> - Add RB from Atish
> - Fixed checkpatch issues missed in v1
> - Replaced Ludovic email address with the rivos one
>
>  hw/riscv/virt.c    |  20 +++--
>  target/riscv/cpu.c | 217 +++++++++++++++++++++++++++++++++++++++++++--
>  target/riscv/cpu.h |  25 ++++++
>  target/riscv/csr.c |  13 ++-
>  4 files changed, 256 insertions(+), 19 deletions(-)
>
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index a5bc7353b4..9bb5ba7366 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -228,7 +228,8 @@ static void create_fdt_socket_cpus(RISCVVirtState *s,
> int socket,
>      int cpu;
>      uint32_t cpu_phandle;
>      MachineState *mc = MACHINE(s);
> -    char *name, *cpu_name, *core_name, *intc_name;
> +    uint8_t satp_mode_max;
> +    char *name, *cpu_name, *core_name, *intc_name, *sv_name;
>
>      for (cpu = s->soc[socket].num_harts - 1; cpu >= 0; cpu--) {
>          cpu_phandle = (*phandle)++;
> @@ -236,14 +237,15 @@ static void create_fdt_socket_cpus(RISCVVirtState
> *s, int socket,
>          cpu_name = g_strdup_printf("/cpus/cpu@%d",
>              s->soc[socket].hartid_base + cpu);
>          qemu_fdt_add_subnode(mc->fdt, cpu_name);
> -        if (riscv_feature(&s->soc[socket].harts[cpu].env,
> -                          RISCV_FEATURE_MMU)) {
> -            qemu_fdt_setprop_string(mc->fdt, cpu_name, "mmu-type",
> -                                    (is_32_bit) ? "riscv,sv32" :
> "riscv,sv48");
> -        } else {
> -            qemu_fdt_setprop_string(mc->fdt, cpu_name, "mmu-type",
> -                                    "riscv,none");
> -        }
> +
> +        satp_mode_max = satp_mode_max_from_map(
> +                            s->soc[socket].harts[cpu].cfg.satp_mode.map,
> +                            is_32_bit);
> +        sv_name = g_strdup_printf("riscv,%s",
> +                                  satp_mode_str(satp_mode_max,
> is_32_bit));
> +        qemu_fdt_setprop_string(mc->fdt, cpu_name, "mmu-type", sv_name);
> +        g_free(sv_name);
> +
>          name = riscv_isa_string(&s->soc[socket].harts[cpu]);
>          qemu_fdt_setprop_string(mc->fdt, cpu_name, "riscv,isa", name);
>          g_free(name);
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index d14e95c9dc..639231ce2e 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -27,6 +27,7 @@
>  #include "time_helper.h"
>  #include "exec/exec-all.h"
>  #include "qapi/error.h"
> +#include "qapi/visitor.h"
>  #include "qemu/error-report.h"
>  #include "hw/qdev-properties.h"
>  #include "migration/vmstate.h"
> @@ -199,7 +200,7 @@ static const char * const riscv_intr_names[] = {
>      "reserved"
>  };
>
> -static void register_cpu_props(DeviceState *dev);
> +static void register_cpu_props(Object *obj);
>
>  const char *riscv_cpu_get_trap_name(target_ulong cause, bool async)
>  {
> @@ -237,7 +238,7 @@ static void riscv_any_cpu_init(Object *obj)
>      set_misa(env, MXL_RV64, RVI | RVM | RVA | RVF | RVD | RVC | RVU);
>  #endif
>      set_priv_version(env, PRIV_VERSION_1_12_0);
> -    register_cpu_props(DEVICE(obj));
> +    register_cpu_props(obj);
>  }
>
>  #if defined(TARGET_RISCV64)
> @@ -246,7 +247,7 @@ static void rv64_base_cpu_init(Object *obj)
>      CPURISCVState *env = &RISCV_CPU(obj)->env;
>      /* We set this in the realise function */
>      set_misa(env, MXL_RV64, 0);
> -    register_cpu_props(DEVICE(obj));
> +    register_cpu_props(obj);
>      /* Set latest version of privileged specification */
>      set_priv_version(env, PRIV_VERSION_1_12_0);
>  }
> @@ -279,7 +280,7 @@ static void rv128_base_cpu_init(Object *obj)
>      CPURISCVState *env = &RISCV_CPU(obj)->env;
>      /* We set this in the realise function */
>      set_misa(env, MXL_RV128, 0);
> -    register_cpu_props(DEVICE(obj));
> +    register_cpu_props(obj);
>      /* Set latest version of privileged specification */
>      set_priv_version(env, PRIV_VERSION_1_12_0);
>  }
> @@ -289,7 +290,7 @@ static void rv32_base_cpu_init(Object *obj)
>      CPURISCVState *env = &RISCV_CPU(obj)->env;
>      /* We set this in the realise function */
>      set_misa(env, MXL_RV32, 0);
> -    register_cpu_props(DEVICE(obj));
> +    register_cpu_props(obj);
>      /* Set latest version of privileged specification */
>      set_priv_version(env, PRIV_VERSION_1_12_0);
>  }
> @@ -342,7 +343,7 @@ static void riscv_host_cpu_init(Object *obj)
>  #elif defined(TARGET_RISCV64)
>      set_misa(env, MXL_RV64, 0);
>  #endif
> -    register_cpu_props(DEVICE(obj));
> +    register_cpu_props(obj);
>  }
>  #endif
>
> @@ -612,6 +613,71 @@ static void riscv_cpu_disas_set_info(CPUState *s,
> disassemble_info *info)
>      }
>  }
>
> +#define OFFSET_SATP_MODE_64     16
> +
> +static uint8_t idx_satp_mode_from_str(const char *satp_mode_str)
> +{
> +    if (!strncmp(satp_mode_str, "mbare", 5)) {
> +        return VM_1_10_MBARE;
> +    }
> +
> +    if (!strncmp(satp_mode_str, "sv32", 4)) {
> +        return VM_1_10_SV32;
> +    }
> +
> +    if (!strncmp(satp_mode_str, "sv39", 4)) {
> +        return VM_1_10_SV39 + OFFSET_SATP_MODE_64;
> +    }
> +
> +    if (!strncmp(satp_mode_str, "sv48", 4)) {
> +        return VM_1_10_SV48 + OFFSET_SATP_MODE_64;
> +    }
> +
> +    if (!strncmp(satp_mode_str, "sv57", 4)) {
> +        return VM_1_10_SV57 + OFFSET_SATP_MODE_64;
> +    }
> +
> +    if (!strncmp(satp_mode_str, "sv64", 4)) {
> +        return VM_1_10_SV64 + OFFSET_SATP_MODE_64;
> +    }
> +
> +    /* Will never get there */
> +    return -1;
> +}
> +
> +uint8_t satp_mode_max_from_map(uint32_t map, bool is_32_bit)
> +{
> +    return is_32_bit ?
> +        (31 - __builtin_clz(map & 0xFFFF)) : (31 - __builtin_clz(map >>
> 16));
> +}
> +
> +const char *satp_mode_str(uint8_t satp_mode, bool is_32_bit)
> +{
> +    if (is_32_bit) {
> +        switch (satp_mode) {
> +        case VM_1_10_SV32:
> +            return "sv32";
> +        case VM_1_10_MBARE:
> +            return "none";
> +        }
> +    } else {
> +        switch (satp_mode) {
> +        case VM_1_10_SV64:
> +            return "sv64";
> +        case VM_1_10_SV57:
> +            return "sv57";
> +        case VM_1_10_SV48:
> +            return "sv48";
> +        case VM_1_10_SV39:
> +            return "sv39";
> +        case VM_1_10_MBARE:
> +            return "none";
> +        }
> +    }
> +
> +    return NULL;
> +}
> +
>  static void riscv_cpu_realize(DeviceState *dev, Error **errp)
>  {
>      CPUState *cs = CPU(dev);
> @@ -907,6 +973,30 @@ static void riscv_cpu_realize(DeviceState *dev, Error
> **errp)
>       }
>  #endif
>
> +    bool rv32 = riscv_cpu_mxl(&cpu->env) == MXL_RV32;
> +
> +    /*
> +     * If unset by both the user and the cpu, we fallback to sv32 for
> 32-bit
> +     * or sv57 for 64-bit when a MMU is present, and bare otherwise.
> +     */
> +    if (cpu->cfg.satp_mode.map == 0) {
> +        if (riscv_feature(&cpu->env, RISCV_FEATURE_MMU)) {
> +            if (rv32) {
> +                cpu->cfg.satp_mode.map |= (1 <<
> idx_satp_mode_from_str("sv32"));
> +            } else {
> +                cpu->cfg.satp_mode.map |= (1 <<
> idx_satp_mode_from_str("sv57"));
> +            }
> +        } else {
> +            cpu->cfg.satp_mode.map |= (1 <<
> idx_satp_mode_from_str("mbare"));
> +        }
> +    }
> +
> +    riscv_cpu_finalize_features(cpu, &local_err);
> +    if (local_err != NULL) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +
>      riscv_cpu_register_gdb_regs_for_features(cs);
>
>      qemu_init_vcpu(cs);
> @@ -915,6 +1005,115 @@ static void riscv_cpu_realize(DeviceState *dev,
> Error **errp)
>      mcc->parent_realize(dev, errp);
>  }
>
> +static void cpu_riscv_get_satp(Object *obj, Visitor *v, const char *name,
> +                           void *opaque, Error **errp)
> +{
> +    RISCVSATPMap *satp_map = opaque;
> +    uint8_t idx_satp = idx_satp_mode_from_str(name);
> +    bool value;
> +
> +    value = (satp_map->map & (1 << idx_satp));
> +
> +    visit_type_bool(v, name, &value, errp);
> +}
> +
> +static void cpu_riscv_set_satp(Object *obj, Visitor *v, const char *name,
> +                           void *opaque, Error **errp)
> +{
> +    RISCVSATPMap *satp_map = opaque;
> +    uint8_t idx_satp = idx_satp_mode_from_str(name);
> +    bool value;
> +
> +    if (!visit_type_bool(v, name, &value, errp)) {
> +        return;
> +    }
> +
> +    if (value) {
> +        satp_map->map |= 1 << idx_satp;
> +    }
> +
> +    satp_map->init |= 1 << idx_satp;
> +}
> +
> +static void riscv_add_satp_mode_properties(Object *obj)
> +{
> +    RISCVCPU *cpu = RISCV_CPU(obj);
> +
> +    object_property_add(obj, "mbare", "bool", cpu_riscv_get_satp,
> +                        cpu_riscv_set_satp, NULL, &cpu->cfg.satp_mode);
> +    object_property_add(obj, "sv32", "bool", cpu_riscv_get_satp,
> +                        cpu_riscv_set_satp, NULL, &cpu->cfg.satp_mode);
> +    object_property_add(obj, "sv39", "bool", cpu_riscv_get_satp,
> +                        cpu_riscv_set_satp, NULL, &cpu->cfg.satp_mode);
> +    object_property_add(obj, "sv48", "bool", cpu_riscv_get_satp,
> +                        cpu_riscv_set_satp, NULL, &cpu->cfg.satp_mode);
> +    object_property_add(obj, "sv57", "bool", cpu_riscv_get_satp,
> +                        cpu_riscv_set_satp, NULL, &cpu->cfg.satp_mode);
> +    object_property_add(obj, "sv64", "bool", cpu_riscv_get_satp,
> +                        cpu_riscv_set_satp, NULL, &cpu->cfg.satp_mode);
> +}
> +
> +#define error_append_or_setg(errp, str, ...) ({             \
> +        if (*errp)                                          \
> +            error_append_hint(errp, str"\n", ##__VA_ARGS__);\
> +        else                                                \
> +            error_setg(errp, str, ##__VA_ARGS__);           \
> +    })
> +
> +void riscv_cpu_satp_mode_finalize(RISCVCPU *cpu, Error **errp)
> +{
> +    bool rv32 = riscv_cpu_mxl(&cpu->env) == MXL_RV32;
> +
> +    /* Get rid of 32-bit/64-bit incompatibility */
> +    if (rv32) {
> +        if (cpu->cfg.satp_mode.map >= (1 << OFFSET_SATP_MODE_64))
> +            error_append_or_setg(errp, "cannot enable 64-bit satp modes "
> +                                 "(sv39/sv48/sv57/sv64) if cpu is in
> 32-bit "
> +                                 "mode");
> +    } else {
> +        if (cpu->cfg.satp_mode.map & (1 << VM_1_10_SV32))
> +            error_append_or_setg(errp, "cannot enable 32-bit satp mode
> (sv32) "
> +                                 "if cpu is in 64-bit mode");
> +    }
> +
> +    /*
> +     * Then make sure the user did not ask for an invalid configuration
> as per
> +     * the specification.
> +     */
> +    if (rv32) {
> +        if (cpu->cfg.satp_mode.map & (1 << VM_1_10_SV32)) {
> +            if (!(cpu->cfg.satp_mode.map & (1 << VM_1_10_MBARE)) &&
> +                 (cpu->cfg.satp_mode.init & (1 << VM_1_10_MBARE)))
> +                error_append_or_setg(errp, "cannot disable mbare satp
> mode if "
> +                                     "sv32 is enabled");
> +        }
> +    } else {
> +        uint8_t satp_mode_max;
> +
> +        satp_mode_max = satp_mode_max_from_map(cpu->cfg.satp_mode.map,
> false);
> +
> +        for (int i = satp_mode_max - 1; i >= 0; --i) {
> +            if (!(cpu->cfg.satp_mode.map & (1 << (i +
> OFFSET_SATP_MODE_64))) &&
> +                 (cpu->cfg.satp_mode.init & (1 << (i +
> OFFSET_SATP_MODE_64))))
> +                error_append_or_setg(errp, "cannot disable %s satp mode
> if %s "
> +                                     "is enabled",
> +                                     satp_mode_str(i, false),
> +                                     satp_mode_str(satp_mode_max, false));
> +        }
> +    }
> +}
> +
> +void riscv_cpu_finalize_features(RISCVCPU *cpu, Error **errp)
> +{
> +    Error *local_err = NULL;
> +
> +    riscv_cpu_satp_mode_finalize(cpu, &local_err);
> +    if (local_err != NULL) {
> +        error_propagate(errp, local_err);
> +        return;
> +    }
> +}
> +
>  #ifndef CONFIG_USER_ONLY
>  static void riscv_cpu_set_irq(void *opaque, int irq, int level)
>  {
> @@ -1070,13 +1269,16 @@ static Property riscv_cpu_extensions[] = {
>      DEFINE_PROP_END_OF_LIST(),
>  };
>
> -static void register_cpu_props(DeviceState *dev)
> +static void register_cpu_props(Object *obj)
>  {
>      Property *prop;
> +    DeviceState *dev = DEVICE(obj);
>
>      for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {
>          qdev_property_add_static(dev, prop);
>      }
> +
> +    riscv_add_satp_mode_properties(obj);
>  }
>
>  static Property riscv_cpu_properties[] = {
> @@ -1094,6 +1296,7 @@ static Property riscv_cpu_properties[] = {
>
>      DEFINE_PROP_BOOL("rvv_ta_all_1s", RISCVCPU, cfg.rvv_ta_all_1s, false),
>      DEFINE_PROP_BOOL("rvv_ma_all_1s", RISCVCPU, cfg.rvv_ma_all_1s, false),
> +
>      DEFINE_PROP_END_OF_LIST(),
>  };
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 3a9e25053f..1717b33321 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -27,6 +27,7 @@
>  #include "qom/object.h"
>  #include "qemu/int128.h"
>  #include "cpu_bits.h"
> +#include "qapi/qapi-types-common.h"
>
>  #define TCG_GUEST_DEFAULT_MO 0
>
> @@ -407,6 +408,22 @@ struct RISCVCPUClass {
>      DeviceReset parent_reset;
>  };
>
> +/*
> + * map and init are divided into two 16bit bitmaps: the upper one is for
> rv64
> + * and the lower one is for rv32, this is because the value for sv32 (ie.
> 1)
> + * may be reused later for another purpose for rv64 (see the
> specification which
> + * states that it is "reserved for standard use").
> + *
> + * In a 16bit bitmap in map, the most significant set bit is the maximum
> + * satp mode that is supported.
> + *
> + * Both 16bit bitmaps in init are used to make sure the user selected a
> correct
> + * combination as per the specification.
> + */
> +typedef struct {
> +    uint32_t map, init;
> +} RISCVSATPMap;
> +
>  struct RISCVCPUConfig {
>      bool ext_i;
>      bool ext_e;
> @@ -480,6 +497,8 @@ struct RISCVCPUConfig {
>      bool debug;
>
>      bool short_isa_string;
> +
> +    RISCVSATPMap satp_mode;
>  };
>
>  typedef struct RISCVCPUConfig RISCVCPUConfig;
> @@ -789,4 +808,10 @@ void riscv_set_csr_ops(int csrno,
> riscv_csr_operations *ops);
>
>  void riscv_cpu_register_gdb_regs_for_features(CPUState *cs);
>
> +uint8_t satp_mode_max_from_map(uint32_t map, bool is_32_bit);
> +const char *satp_mode_str(uint8_t satp_mode, bool is_32_bit);
> +
> +void riscv_cpu_satp_mode_finalize(RISCVCPU *cpu, Error **errp);
> +void riscv_cpu_finalize_features(RISCVCPU *cpu, Error **errp);
> +
>  #endif /* RISCV_CPU_H */
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 5c9a7ee287..5c732653b2 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -1109,10 +1109,17 @@ static RISCVException read_mstatus(CPURISCVState
> *env, int csrno,
>
>  static int validate_vm(CPURISCVState *env, target_ulong vm)
>  {
> -    if (riscv_cpu_mxl(env) == MXL_RV32) {
> -        return valid_vm_1_10_32[vm & 0xf];
> +    uint8_t satp_mode_max;
> +    RISCVCPU *cpu = RISCV_CPU(env_cpu(env));
> +    bool is_32_bit = riscv_cpu_mxl(env) == MXL_RV32;
> +
> +    vm &= 0xf;
> +    satp_mode_max = satp_mode_max_from_map(cpu->cfg.satp_mode.map,
> is_32_bit);
> +
> +    if (is_32_bit) {
> +        return valid_vm_1_10_32[vm] && (vm <= satp_mode_max);
>      } else {
> -        return valid_vm_1_10_64[vm & 0xf];
> +        return valid_vm_1_10_64[vm] && (vm <= satp_mode_max);
>      }
>  }
>
> --
> 2.37.2
>
>
>

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