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Re: [RFC PATCH v4 1/4] target/riscv: Add smstateen support


From: Tsukasa OI
Subject: Re: [RFC PATCH v4 1/4] target/riscv: Add smstateen support
Date: Fri, 13 May 2022 18:55:02 +0900

On 2022/05/13 17:51, Mayuresh Chitale wrote:
> Smstateen extension specifies a mechanism to close
> the potential covert channels that could cause security issues.
> 
> This patch adds the CSRs defined in the specification and
> the corresponding predicates and read/write functions.
> 
> Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
> ---
>  target/riscv/cpu.c      |   2 +
>  target/riscv/cpu.h      |   4 +
>  target/riscv/cpu_bits.h |  36 +++++++
>  target/riscv/csr.c      | 210 ++++++++++++++++++++++++++++++++++++++++
>  target/riscv/machine.c  |  21 ++++
>  5 files changed, 273 insertions(+)
> 
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 25a4ba3e22..3be2c644f9 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -870,6 +870,7 @@ static Property riscv_cpu_properties[] = {
>      DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true),
>      DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true),
>      DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
> +    DEFINE_PROP_BOOL("smstateen", RISCVCPU, cfg.ext_smstateen, false),
>  
>      DEFINE_PROP_STRING("priv_spec", RISCVCPU, cfg.priv_spec),
>      DEFINE_PROP_STRING("vext_spec", RISCVCPU, cfg.vext_spec),
> @@ -1062,6 +1063,7 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char 
> **isa_str, int max_str_len)
>          ISA_EDATA_ENTRY(svinval, ext_svinval),
>          ISA_EDATA_ENTRY(svnapot, ext_svnapot),
>          ISA_EDATA_ENTRY(svpbmt, ext_svpbmt),
> +        ISA_EDATA_ENTRY(smstateen, ext_smstateen),

isa_edata_arr must be arranged by canonical ordering.
In this case, following comment (above those entries) applies:

>      * 3. Standard supervisor-level extensions (starts with 'S') should be
>      *    listed after standard unprivileged extensions.  If multiple
>      *    supervisor-level extensions are listed, they should be ordered
>      *    alphabetically.

That means, you should put Smstateen extension line between zve64f and
svinval.  Other than that, your changes looks good to me.

Thanks,

Tsukasa

>      };
>  
>      for (i = 0; i < ARRAY_SIZE(isa_edata_arr); i++) {
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index a55c918274..d6fdc63ff2 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -327,6 +327,9 @@ struct CPUArchState {
>  
>      /* CSRs for execution enviornment configuration */
>      uint64_t menvcfg;
> +    uint64_t mstateen[SMSTATEEN_MAX_COUNT];
> +    uint64_t hstateen[SMSTATEEN_MAX_COUNT];
> +    uint64_t sstateen[SMSTATEEN_MAX_COUNT];
>      target_ulong senvcfg;
>      uint64_t henvcfg;
>  #endif
> @@ -411,6 +414,7 @@ struct RISCVCPUConfig {
>      bool ext_zhinxmin;
>      bool ext_zve32f;
>      bool ext_zve64f;
> +    bool ext_smstateen;
>  
>      uint32_t mvendorid;
>      uint64_t marchid;
> diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> index 4a55c6a709..2a3ef26d21 100644
> --- a/target/riscv/cpu_bits.h
> +++ b/target/riscv/cpu_bits.h
> @@ -208,6 +208,12 @@
>  /* Supervisor Configuration CSRs */
>  #define CSR_SENVCFG         0x10A
>  
> +/* Supervisor state CSRs */
> +#define CSR_SSTATEEN0       0x10C
> +#define CSR_SSTATEEN1       0x10D
> +#define CSR_SSTATEEN2       0x10E
> +#define CSR_SSTATEEN3       0x10F
> +
>  /* Supervisor Trap Handling */
>  #define CSR_SSCRATCH        0x140
>  #define CSR_SEPC            0x141
> @@ -257,6 +263,16 @@
>  #define CSR_HENVCFG         0x60A
>  #define CSR_HENVCFGH        0x61A
>  
> +/* Hypervisor state CSRs */
> +#define CSR_HSTATEEN0       0x60C
> +#define CSR_HSTATEEN0H      0x61C
> +#define CSR_HSTATEEN1       0x60D
> +#define CSR_HSTATEEN1H      0x61D
> +#define CSR_HSTATEEN2       0x60E
> +#define CSR_HSTATEEN2H      0x61E
> +#define CSR_HSTATEEN3       0x60F
> +#define CSR_HSTATEEN3H      0x61F
> +
>  /* Virtual CSRs */
>  #define CSR_VSSTATUS        0x200
>  #define CSR_VSIE            0x204
> @@ -304,6 +320,26 @@
>  #define CSR_MENVCFG         0x30A
>  #define CSR_MENVCFGH        0x31A
>  
> +/* Machine state CSRs */
> +#define CSR_MSTATEEN0       0x30C
> +#define CSR_MSTATEEN0H      0x31C
> +#define CSR_MSTATEEN1       0x30D
> +#define CSR_MSTATEEN1H      0x31D
> +#define CSR_MSTATEEN2       0x30E
> +#define CSR_MSTATEEN2H      0x31E
> +#define CSR_MSTATEEN3       0x30F
> +#define CSR_MSTATEEN3H      0x31F
> +
> +/* Common defines for all smstateen */
> +#define SMSTATEEN_MAX_COUNT 4
> +#define SMSTATEEN0_CS       0
> +#define SMSTATEEN0_FCSR     0
> +#define SMSTATEEN0_IMSIC    58
> +#define SMSTATEEN0_AIA      59
> +#define SMSTATEEN0_SVSLCT   60
> +#define SMSTATEEN0_HSENVCFG 62
> +#define SMSTATEEN_STATEN    63
> +
>  /* Enhanced Physical Memory Protection (ePMP) */
>  #define CSR_MSECCFG         0x747
>  #define CSR_MSECCFGH        0x757
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index e144ce7135..fea5cdd178 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -247,6 +247,42 @@ static RISCVException hmode32(CPURISCVState *env, int 
> csrno)
>  
>  }
>  
> +static RISCVException mstateen(CPURISCVState *env, int csrno)
> +{
> +    CPUState *cs = env_cpu(env);
> +    RISCVCPU *cpu = RISCV_CPU(cs);
> +
> +    if (!cpu->cfg.ext_smstateen) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    return any(env, csrno);
> +}
> +
> +static RISCVException hstateen(CPURISCVState *env, int csrno)
> +{
> +    CPUState *cs = env_cpu(env);
> +    RISCVCPU *cpu = RISCV_CPU(cs);
> +
> +    if (!cpu->cfg.ext_smstateen) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    return hmode(env, csrno);
> +}
> +
> +static RISCVException sstateen(CPURISCVState *env, int csrno)
> +{
> +    CPUState *cs = env_cpu(env);
> +    RISCVCPU *cpu = RISCV_CPU(cs);
> +
> +    if (!cpu->cfg.ext_smstateen) {
> +        return RISCV_EXCP_ILLEGAL_INST;
> +    }
> +
> +    return smode(env, csrno);
> +}
> +
>  /* Checks if PointerMasking registers could be accessed */
>  static RISCVException pointer_masking(CPURISCVState *env, int csrno)
>  {
> @@ -1574,6 +1610,129 @@ static RISCVException write_henvcfgh(CPURISCVState 
> *env, int csrno,
>      return RISCV_EXCP_NONE;
>  }
>  
> +static inline void write_smstateen(CPURISCVState *env, uint64_t *reg,
> +                                   uint64_t wr_mask, uint64_t new_val)
> +{
> +    *reg = (*reg & ~wr_mask) | (new_val & wr_mask);
> +}
> +
> +static RISCVException read_mstateen(CPURISCVState *env, int csrno,
> +                                    target_ulong *val)
> +{
> +    *val = env->mstateen[csrno - CSR_MSTATEEN0];
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mstateen(CPURISCVState *env, int csrno,
> +                                     target_ulong new_val)
> +{
> +    uint64_t *reg;
> +    uint64_t wr_mask = 1UL << SMSTATEEN_STATEN;
> +
> +    reg = &env->mstateen[csrno - CSR_MSTATEEN0];
> +    write_smstateen(env, reg, wr_mask, new_val);
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_mstateenh(CPURISCVState *env, int csrno,
> +                                     target_ulong *val)
> +{
> +    *val = env->mstateen[csrno - CSR_MSTATEEN0H] >> 32;
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_mstateenh(CPURISCVState *env, int csrno,
> +                                      target_ulong new_val)
> +{
> +    uint64_t *reg;
> +    uint64_t val;
> +    uint64_t wr_mask = 1UL << SMSTATEEN_STATEN;
> +
> +    reg = &env->mstateen[csrno - CSR_MSTATEEN0H];
> +    val = (uint64_t)new_val << 32;
> +    val |= *reg & 0xFFFFFFFF;
> +    write_smstateen(env, reg, wr_mask, val);
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_hstateen(CPURISCVState *env, int csrno,
> +                                    target_ulong *val)
> +{
> +    *val = env->hstateen[csrno - CSR_HSTATEEN0];
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_hstateen(CPURISCVState *env, int csrno,
> +                                     target_ulong new_val)
> +{
> +    uint64_t *reg;
> +    uint64_t wr_mask = 1UL << SMSTATEEN_STATEN;
> +    int index = csrno - CSR_HSTATEEN0;
> +
> +    reg = &env->hstateen[index];
> +    wr_mask &= env->mstateen[index];
> +    write_smstateen(env, reg, wr_mask, new_val);
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_hstateenh(CPURISCVState *env, int csrno,
> +                                     target_ulong *val)
> +{
> +    *val = env->hstateen[csrno - CSR_HSTATEEN0H] >> 32;
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_hstateenh(CPURISCVState *env, int csrno,
> +                                      target_ulong new_val)
> +{
> +    uint64_t *reg;
> +    uint64_t val;
> +    uint64_t wr_mask = 1UL << SMSTATEEN_STATEN;
> +    int index = csrno - CSR_HSTATEEN0H;
> +
> +    reg = &env->hstateen[index];
> +    val = (uint64_t)new_val << 32;
> +    val |= *reg & 0xFFFFFFFF;
> +    wr_mask &= env->mstateen[index];
> +
> +    write_smstateen(env, reg, wr_mask, val);
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException read_sstateen(CPURISCVState *env, int csrno,
> +                                    target_ulong *val)
> +{
> +    *val = env->sstateen[csrno - CSR_SSTATEEN0];
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException write_sstateen(CPURISCVState *env, int csrno,
> +                                     target_ulong new_val)
> +{
> +    uint64_t *reg;
> +    uint64_t wr_mask = 0;
> +    int index = csrno - CSR_SSTATEEN0;
> +    bool virt = riscv_cpu_virt_enabled(env);
> +
> +    reg = &env->sstateen[index];
> +    if (virt) {
> +        wr_mask &= env->mstateen[index];
> +    } else {
> +        wr_mask &= env->hstateen[index];
> +    }
> +    write_smstateen(env, reg, wr_mask, new_val);
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
>  static RISCVException rmw_mip64(CPURISCVState *env, int csrno,
>                                  uint64_t *ret_val,
>                                  uint64_t new_val, uint64_t wr_mask)
> @@ -3441,6 +3600,57 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_HENVCFGH] = { "henvcfgh", hmode32, read_henvcfgh, write_henvcfgh,
>                                            .min_priv_ver = 
> PRIV_VERSION_1_12_0 },
>  
> +    /* Smstateen extension CSRs */
> +    [CSR_MSTATEEN0] = { "mstateen0", mstateen, read_mstateen, write_mstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN0H] = { "mstateen0h", mstateen, read_mstateenh,
> +                          write_mstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN1] = { "mstateen1", mstateen, read_mstateen, write_mstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN1H] = { "mstateen1h", mstateen, read_mstateenh,
> +                          write_mstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN2] = { "mstateen2", mstateen, read_mstateen, write_mstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN2H] = { "mstateen2h", mstateen, read_mstateenh,
> +                          write_mstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN3] = { "mstateen3", mstateen, read_mstateen, write_mstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_MSTATEEN3H] = { "mstateen3h", mstateen, read_mstateenh,
> +                          write_mstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +
> +    [CSR_HSTATEEN0] = { "hstateen0", hstateen, read_hstateen, write_hstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN0H] = { "hstateen0h", hstateen, read_hstateenh,
> +                          write_hstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN1] = { "hstateen1", hstateen, read_hstateen, write_hstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN1H] = { "hstateen1h", hstateen, read_hstateenh,
> +                          write_hstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN2] = { "hstateen2", hstateen, read_hstateen, write_hstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN2H] = { "hstateen2h", hstateen, read_hstateenh,
> +                          write_hstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN3] = { "hstateen3", hstateen, read_hstateen, write_hstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_HSTATEEN3H] = { "hstateen3h", hstateen, read_hstateenh,
> +                          write_hstateenh,
> +                          .min_priv_ver = PRIV_VERSION_1_12_0 },
> +
> +    [CSR_SSTATEEN0] = { "sstateen0", sstateen, read_sstateen, write_sstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_SSTATEEN1] = { "sstateen1", sstateen, read_sstateen, write_sstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_SSTATEEN2] = { "sstateen2", sstateen, read_sstateen, write_sstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
> +    [CSR_SSTATEEN3] = { "sstateen3", sstateen, read_sstateen, write_sstateen,
> +                         .min_priv_ver = PRIV_VERSION_1_12_0 },
>      /* Supervisor Trap Setup */
>      [CSR_SSTATUS]    = { "sstatus",    smode, read_sstatus,    
> write_sstatus, NULL,
>                                                read_sstatus_i128              
>    },
> diff --git a/target/riscv/machine.c b/target/riscv/machine.c
> index 2a437b29a1..84a75dbb08 100644
> --- a/target/riscv/machine.c
> +++ b/target/riscv/machine.c
> @@ -262,6 +262,26 @@ static int riscv_cpu_post_load(void *opaque, int 
> version_id)
>      return 0;
>  }
>  
> +static bool smstateen_needed(void *opaque)
> +{
> +    RISCVCPU *cpu = opaque;
> +
> +    return cpu->cfg.ext_smstateen;
> +}
> +
> +static const VMStateDescription vmstate_smstateen = {
> +    .name = "cpu/smtateen",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = smstateen_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT64_ARRAY(env.mstateen, RISCVCPU, 4),
> +        VMSTATE_UINT64_ARRAY(env.hstateen, RISCVCPU, 4),
> +        VMSTATE_UINT64_ARRAY(env.sstateen, RISCVCPU, 4),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static bool envcfg_needed(void *opaque)
>  {
>      RISCVCPU *cpu = opaque;
> @@ -347,6 +367,7 @@ const VMStateDescription vmstate_riscv_cpu = {
>          &vmstate_kvmtimer,
>          &vmstate_envcfg,
>          &vmstate_debug,
> +        &vmstate_smstateen,
>          NULL
>      }
>  };



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