Re: [PATCH 3/3] target/riscv/kvm: get/set vector vregs[]

[Alistair Francis]

On Wed, Jan 24, 2024 at 2:18 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> vregs[] have variable size that depends on the current vlenb set by the
> host, meaning we can't use our regular kvm_riscv_reg_id() to retrieve
> it.
>
> Create a generic kvm_encode_reg_size_id() helper to encode any given
> size in bytes into a given kvm reg id. kvm_riscv_vector_reg_id() will
> use it to encode vlenb into a given vreg ID.
>
> kvm_riscv_(get|set)_vector() can then get/set all 32 vregs.
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Acked-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/kvm/kvm-cpu.c | 57 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 55 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
> index 3812481971..a7881de7f9 100644
> --- a/target/riscv/kvm/kvm-cpu.c
> +++ b/target/riscv/kvm/kvm-cpu.c
> @@ -86,6 +86,27 @@ static uint64_t kvm_riscv_reg_id_u64(uint64_t type, 
> uint64_t idx)
>      return KVM_REG_RISCV | KVM_REG_SIZE_U64 | type | idx;
>  }
>
> +static uint64_t kvm_encode_reg_size_id(uint64_t id, size_t size_b)
> +{
> +    uint64_t size_ctz = __builtin_ctz(size_b);
> +
> +    return id | (size_ctz << KVM_REG_SIZE_SHIFT);
> +}
> +
> +static uint64_t kvm_riscv_vector_reg_id(RISCVCPU *cpu,
> +                                        uint64_t idx)
> +{
> +    uint64_t id;
> +    size_t size_b;
> +
> +    g_assert(idx < 32);
> +
> +    id = KVM_REG_RISCV | KVM_REG_RISCV_VECTOR | 
> KVM_REG_RISCV_VECTOR_REG(idx);
> +    size_b = cpu->cfg.vlenb;
> +
> +    return kvm_encode_reg_size_id(id, size_b);
> +}
> +
>  #define RISCV_CORE_REG(env, name) \
>      kvm_riscv_reg_id_ulong(env, KVM_REG_RISCV_CORE, \
>                             KVM_REG_RISCV_CORE_REG(name))
> @@ -694,7 +715,8 @@ static int kvm_riscv_get_regs_vector(CPUState *cs)
>      RISCVCPU *cpu = RISCV_CPU(cs);
>      CPURISCVState *env = &cpu->env;
>      target_ulong reg;
> -    int ret = 0;
> +    uint64_t vreg_id;
> +    int vreg_idx, ret = 0;
>
>      if (!riscv_has_ext(env, RVV)) {
>          return 0;
> @@ -724,6 +746,21 @@ static int kvm_riscv_get_regs_vector(CPUState *cs)
>              return ret;
>          }
>          cpu->cfg.vlenb = reg;
> +
> +        for (int i = 0; i < 32; i++) {
> +            /*
> +             * vreg[] is statically allocated using RV_VLEN_MAX.
> +             * Use it instead of vlenb to calculate vreg_idx for
> +             * simplicity.
> +             */
> +            vreg_idx = i * RV_VLEN_MAX / 64;
> +            vreg_id = kvm_riscv_vector_reg_id(cpu, i);
> +
> +            ret = kvm_get_one_reg(cs, vreg_id, &env->vreg[vreg_idx]);
> +            if (ret) {
> +                return ret;
> +            }
> +        }
>      }
>
>      return 0;
> @@ -734,7 +771,8 @@ static int kvm_riscv_put_regs_vector(CPUState *cs)
>      RISCVCPU *cpu = RISCV_CPU(cs);
>      CPURISCVState *env = &cpu->env;
>      target_ulong reg;
> -    int ret = 0;
> +    uint64_t vreg_id;
> +    int vreg_idx, ret = 0;
>
>      if (!riscv_has_ext(env, RVV)) {
>          return 0;
> @@ -761,6 +799,21 @@ static int kvm_riscv_put_regs_vector(CPUState *cs)
>      if (kvm_v_vlenb.supported) {
>          reg = cpu->cfg.vlenb;
>          ret = kvm_set_one_reg(cs, RISCV_VECTOR_CSR_REG(env, vlenb), &reg);
> +
> +        for (int i = 0; i < 32; i++) {
> +            /*
> +             * vreg[] is statically allocated using RV_VLEN_MAX.
> +             * Use it instead of vlenb to calculate vreg_idx for
> +             * simplicity.
> +             */
> +            vreg_idx = i * RV_VLEN_MAX / 64;
> +            vreg_id = kvm_riscv_vector_reg_id(cpu, i);
> +
> +            ret = kvm_set_one_reg(cs, vreg_id, &env->vreg[vreg_idx]);
> +            if (ret) {
> +                return ret;
> +            }
> +        }
>      }
>
>      return ret;
> --
> 2.43.0
>
>