Re: [PATCH] target/riscv: Support configuarable marchid, mvendorid, mipid CSR values

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

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On Tue, Apr 19, 2022 at 1:27 PM Anup Patel <apatel@ventanamicro.com> wrote:

> On Tue, Apr 19, 2022 at 10:52 AM Alistair Francis <alistair23@gmail.com>
> wrote:
> >
> > On Fri, Apr 15, 2022 at 7:37 PM <frank.chang@sifive.com> wrote:
> > >
> > > From: Frank Chang <frank.chang@sifive.com>
> > >
> > > Allow user to set core's marchid, mvendorid, mipid CSRs through
> > > -cpu command line option.
> > >
> > > Signed-off-by: Frank Chang <frank.chang@sifive.com>
> > > Reviewed-by: Jim Shu <jim.shu@sifive.com>
> > > ---
> > >  target/riscv/cpu.c |  4 ++++
> > >  target/riscv/cpu.h |  4 ++++
> > >  target/riscv/csr.c | 38 ++++++++++++++++++++++++++++++++++----
> > >  3 files changed, 42 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> > > index ddda4906ff..2eea0f9be7 100644
> > > --- a/target/riscv/cpu.c
> > > +++ b/target/riscv/cpu.c
> > > @@ -786,6 +786,10 @@ static Property riscv_cpu_properties[] = {
> > >      DEFINE_PROP_UINT16("vlen", RISCVCPU, cfg.vlen, 128),
> > >      DEFINE_PROP_UINT16("elen", RISCVCPU, cfg.elen, 64),
> > >
> > > +    DEFINE_PROP_UINT32("mvendorid", RISCVCPU, cfg.mvendorid, 0),
> > > +    DEFINE_PROP_UINT64("marchid", RISCVCPU, cfg.marchid, 0),
> > > +    DEFINE_PROP_UINT64("mipid", RISCVCPU, cfg.mipid, 0),
> >
> > Should we have non-zero defaults here?
>
> To do that, we need mvendorid for QEMU RISC-V.
>
> The marchid and mipid can be based on the QEMU version number.
>
> Regards,
> Anup
>

The original intention for this patch is to allow users to define
their own $mvendorid, $marchid, and $mipid through the command line
when they initiate QEMU.

If we want to provide the default values for QEMU RISC-V CPU,
just like what Anup said.
We need to define our own mvendorid, which should be a JEDEC manufacturer
ID.
(Perhaps it's fine to just give some random legal JEDEC manufacturer ID
as I don't think we would really want to spend the money on that.)

For $marchid and $mipid,
I agree that it could base on QEMU's version from the QEMU_FULL_VERSION
macro.
(and $marchid should have MSB set to 1 for open-source projects.)

Regards,
Frank Chang


>
> >
> > Alistair
> >
> > > +
> > >      DEFINE_PROP_BOOL("svinval", RISCVCPU, cfg.ext_svinval, false),
> > >      DEFINE_PROP_BOOL("svnapot", RISCVCPU, cfg.ext_svnapot, false),
> > >      DEFINE_PROP_BOOL("svpbmt", RISCVCPU, cfg.ext_svpbmt, false),
> > > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> > > index c069fe85fa..3ab92deb4b 100644
> > > --- a/target/riscv/cpu.h
> > > +++ b/target/riscv/cpu.h
> > > @@ -370,6 +370,10 @@ struct RISCVCPUConfig {
> > >      bool ext_zve32f;
> > >      bool ext_zve64f;
> > >
> > > +    uint32_t mvendorid;
> > > +    uint64_t marchid;
> > > +    uint64_t mipid;
> > > +
> > >      /* Vendor-specific custom extensions */
> > >      bool ext_XVentanaCondOps;
> > >
> > > diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> > > index 341c2e6f23..9a02038adb 100644
> > > --- a/target/riscv/csr.c
> > > +++ b/target/riscv/csr.c
> > > @@ -603,6 +603,36 @@ static RISCVException write_ignore(CPURISCVState
> *env, int csrno,
> > >      return RISCV_EXCP_NONE;
> > >  }
> > >
> > > +static RISCVException read_mvendorid(CPURISCVState *env, int csrno,
> > > +                                     target_ulong *val)
> > > +{
> > > +    CPUState *cs = env_cpu(env);
> > > +    RISCVCPU *cpu = RISCV_CPU(cs);
> > > +
> > > +    *val = cpu->cfg.mvendorid;
> > > +    return RISCV_EXCP_NONE;
> > > +}
> > > +
> > > +static RISCVException read_marchid(CPURISCVState *env, int csrno,
> > > +                                   target_ulong *val)
> > > +{
> > > +    CPUState *cs = env_cpu(env);
> > > +    RISCVCPU *cpu = RISCV_CPU(cs);
> > > +
> > > +    *val = cpu->cfg.marchid;
> > > +    return RISCV_EXCP_NONE;
> > > +}
> > > +
> > > +static RISCVException read_mipid(CPURISCVState *env, int csrno,
> > > +                                 target_ulong *val)
> > > +{
> > > +    CPUState *cs = env_cpu(env);
> > > +    RISCVCPU *cpu = RISCV_CPU(cs);
> > > +
> > > +    *val = cpu->cfg.mipid;
> > > +    return RISCV_EXCP_NONE;
> > > +}
> > > +
> > >  static RISCVException read_mhartid(CPURISCVState *env, int csrno,
> > >                                     target_ulong *val)
> > >  {
> > > @@ -3098,10 +3128,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] =
> {
> > >      [CSR_MINSTRETH] = { "minstreth", any32, read_instreth },
> > >
> > >      /* Machine Information Registers */
> > > -    [CSR_MVENDORID] = { "mvendorid", any,   read_zero    },
> > > -    [CSR_MARCHID]   = { "marchid",   any,   read_zero    },
> > > -    [CSR_MIMPID]    = { "mimpid",    any,   read_zero    },
> > > -    [CSR_MHARTID]   = { "mhartid",   any,   read_mhartid },
> > > +    [CSR_MVENDORID] = { "mvendorid", any,   read_mvendorid },
> > > +    [CSR_MARCHID]   = { "marchid",   any,   read_marchid   },
> > > +    [CSR_MIMPID]    = { "mimpid",    any,   read_mipid     },
> > > +    [CSR_MHARTID]   = { "mhartid",   any,   read_mhartid   },
> > >
> > >      /* Machine Trap Setup */
> > >      [CSR_MSTATUS]     = { "mstatus",    any,   read_mstatus,
>  write_mstatus, NULL,
> > > --
> > > 2.35.1
> > >
> > >
> >
>

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