Re: [PATCH 2/2] target/arm: Implement Neoverse N2 CPU model

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> Implement a model of the Neoverse N2 CPU. This is an Armv9.0-A
> processor very similar to the Cortex-A710. The differences are:
>  * no FEAT_EVT
>  * FEAT_DGH (data gathering hint)
>  * FEAT_NV (not yet implemented in QEMU)
>  * Statistical Profiling Extension (not implemented in QEMU)
>  * 48 bit physical address range, not 40
>  * CTR_EL0.DIC = 1 (no explicit icache cleaning needed)
>  * PMCR_EL0.N = 6 (always 6 PMU counters, not 20)
>
> Because it has 48-bit physical address support, we can use
> this CPU in the sbsa-ref board as well as the virt board.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  docs/system/arm/virt.rst |   1 +
>  hw/arm/sbsa-ref.c        |   1 +
>  hw/arm/virt.c            |   1 +
>  target/arm/tcg/cpu64.c   | 103 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 106 insertions(+)
>
> diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst
> index e1697ac8f48..7c4c80180c6 100644
> --- a/docs/system/arm/virt.rst
> +++ b/docs/system/arm/virt.rst
> @@ -63,6 +63,7 @@ Supported guest CPU types:
>  - ``host`` (with KVM only)
>  - ``neoverse-n1`` (64-bit)
>  - ``neoverse-v1`` (64-bit)
> +- ``neoverse-n2`` (64-bit)
>  - ``max`` (same as ``host`` for KVM; best possible emulation with TCG)
>  
>  Note that the default is ``cortex-a15``, so for an AArch64 guest you must
> diff --git a/hw/arm/sbsa-ref.c b/hw/arm/sbsa-ref.c
> index bc89eb48062..4db287287e1 100644
> --- a/hw/arm/sbsa-ref.c
> +++ b/hw/arm/sbsa-ref.c
> @@ -154,6 +154,7 @@ static const char * const valid_cpus[] = {
>      ARM_CPU_TYPE_NAME("cortex-a72"),
>      ARM_CPU_TYPE_NAME("neoverse-n1"),
>      ARM_CPU_TYPE_NAME("neoverse-v1"),
> +    ARM_CPU_TYPE_NAME("neoverse-n2"),
>      ARM_CPU_TYPE_NAME("max"),
>  };
>  
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 8ad78b23c24..42253462735 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -215,6 +215,7 @@ static const char *valid_cpus[] = {
>      ARM_CPU_TYPE_NAME("a64fx"),
>      ARM_CPU_TYPE_NAME("neoverse-n1"),
>      ARM_CPU_TYPE_NAME("neoverse-v1"),
> +    ARM_CPU_TYPE_NAME("neoverse-n2"),
>  #endif
>      ARM_CPU_TYPE_NAME("cortex-a53"),
>      ARM_CPU_TYPE_NAME("cortex-a57"),
> diff --git a/target/arm/tcg/cpu64.c b/target/arm/tcg/cpu64.c
> index ea43cf3c1ee..370cc82f0ef 100644
> --- a/target/arm/tcg/cpu64.c
> +++ b/target/arm/tcg/cpu64.c
> @@ -963,6 +963,108 @@ static void aarch64_a710_initfn(Object *obj)
>      aarch64_add_sve_properties(obj);
>  }
>  
> +/* Extra IMPDEF regs in the N2 beyond those in the A710 */
> +static const ARMCPRegInfo neoverse_n2_cp_reginfo[] = {
> +    { .name = "CPURNDBR_EL3", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 6, .crn = 15, .crm = 3, .opc2 = 0,
> +      .access = PL3_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
> +    { .name = "CPURNDPEID_EL3", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 6, .crn = 15, .crm = 3, .opc2 = 1,
> +      .access = PL3_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
> +};
> +
> +static void aarch64_neoverse_n2_initfn(Object *obj)
> +{
> +    ARMCPU *cpu = ARM_CPU(obj);
> +
> +    cpu->dtb_compatible = "arm,neoverse-n2";
> +    set_feature(&cpu->env, ARM_FEATURE_V8);
> +    set_feature(&cpu->env, ARM_FEATURE_NEON);
> +    set_feature(&cpu->env, ARM_FEATURE_GENERIC_TIMER);
> +    set_feature(&cpu->env, ARM_FEATURE_AARCH64);
> +    set_feature(&cpu->env, ARM_FEATURE_CBAR_RO);
> +    set_feature(&cpu->env, ARM_FEATURE_EL2);
> +    set_feature(&cpu->env, ARM_FEATURE_EL3);
> +    set_feature(&cpu->env, ARM_FEATURE_PMU);
> +
> +    /* Ordered by Section B.5: AArch64 ID registers */
> +    cpu->midr          = 0x410FD493; /* r0p3 */
> +    cpu->revidr        = 0;
> +    cpu->isar.id_pfr0  = 0x21110131;
> +    cpu->isar.id_pfr1  = 0x00010000; /* GIC filled in later */
> +    cpu->isar.id_dfr0  = 0x16011099;
> +    cpu->id_afr0       = 0;
> +    cpu->isar.id_mmfr0 = 0x10201105;
> +    cpu->isar.id_mmfr1 = 0x40000000;
> +    cpu->isar.id_mmfr2 = 0x01260000;
> +    cpu->isar.id_mmfr3 = 0x02122211;
> +    cpu->isar.id_isar0 = 0x02101110;
> +    cpu->isar.id_isar1 = 0x13112111;
> +    cpu->isar.id_isar2 = 0x21232042;
> +    cpu->isar.id_isar3 = 0x01112131;
> +    cpu->isar.id_isar4 = 0x00010142;
> +    cpu->isar.id_isar5 = 0x11011121; /* with Crypto */
> +    cpu->isar.id_mmfr4 = 0x01021110;
> +    cpu->isar.id_isar6 = 0x01111111;
> +    cpu->isar.mvfr0    = 0x10110222;
> +    cpu->isar.mvfr1    = 0x13211111;
> +    cpu->isar.mvfr2    = 0x00000043;
> +    cpu->isar.id_pfr2  = 0x00000011;
> +    cpu->isar.id_aa64pfr0  = 0x1201111120111112ull; /* GIC filled in later */
> +    cpu->isar.id_aa64pfr1  = 0x0000000000000221ull;
> +    cpu->isar.id_aa64zfr0  = 0x0000110100110021ull; /* with Crypto */
> +    cpu->isar.id_aa64dfr0  = 0x000011f210305619ull;
> +    cpu->isar.id_aa64dfr1  = 0;
> +    cpu->id_aa64afr0       = 0;
> +    cpu->id_aa64afr1       = 0;
> +    cpu->isar.id_aa64isar0 = 0x0221111110212120ull; /* with Crypto */
> +    cpu->isar.id_aa64isar1 = 0x0011111101211052ull;
> +    cpu->isar.id_aa64mmfr0 = 0x0000022200101125ull;
> +    cpu->isar.id_aa64mmfr1 = 0x0000000010212122ull;
> +    cpu->isar.id_aa64mmfr2 = 0x1221011112101011ull;
> +    cpu->clidr             = 0x0000001482000023ull;
> +    cpu->gm_blocksize      = 4;
> +    cpu->ctr               = 0x00000004b444c004ull;
> +    cpu->dcz_blocksize     = 4;
> +    /* TODO FEAT_MPAM: mpamidr_el1 = 0x0000_0001_001e_01ff */

Jonathan mentioned he was hacking about with MPAM so if there is a stub
implementation of the fields it would be nice to add them.

> +
> +    /* Section B.7.2: PMCR_EL0 */
> +    cpu->isar.reset_pmcr_el0 = 0x3000;  /* with 6 counters */
> +
> +    /* Section B.8.9: ICH_VTR_EL2 */
> +    cpu->gic_num_lrs = 4;
> +    cpu->gic_vpribits = 5;
> +    cpu->gic_vprebits = 5;
> +    cpu->gic_pribits = 5;
> +
> +    /* Section 14: Scalable Vector Extensions support */
> +    cpu->sve_vq.supported = 1 << 0;  /* 128bit */
> +
> +    /*
> +     * The Neoverse N2 TRM does not list CCSIDR values.  The layout of
> +     * the caches are in text in Table 7-1, Table 8-1, and Table 9-1.
> +     *
> +     * L1: 4-way set associative 64-byte line size, total 64K.
> +     * L2: 8-way set associative 64 byte line size, total either 512K or 1024K.
> +     */
> +    cpu->ccsidr[0] = make_ccsidr64(4, 64, 64 * KiB);   /* L1 dcache */
> +    cpu->ccsidr[1] = cpu->ccsidr[0];                   /* L1 icache */
> +    cpu->ccsidr[2] = make_ccsidr64(8, 64, 512 * KiB);  /* L2 cache */
> +
> +    /* FIXME: Not documented -- copied from neoverse-v1 */
> +    cpu->reset_sctlr = 0x30c50838;

Hmm reset_sctlr might need to be bigger because being used for sctlr_el3
is a 64 bit entity which has a number of fields:

  - DSSBS,bit[44] to have some sort of impdef value
  - the others all look like architecturally UNKNOWN values

Otherwise I think this is:

  - 3 - RES1 29:28
  - 0 - RES0 + I assume LE EE bit
  - c - RES1 23, EIS 22 (architecturally UNKNOWN on reset)
  - 5 - RES1 18, 16
  - 0 - RES0 15:14, EnDB 13 (architecturally UNKNOWN on reset), I 12 RES0
  - 8 - EOS 11 (architecturally UNKNOWN on reset)
  - 3 - RES1 5:4
  - 8 - SA 3 (architecturally UNKNOWN on reset)

It's a little confusing because the language describing these
architecturally unknown states refers to resetting to EL3 (I assume a
decent firmware would make sure everything is set correctly). Which
makes me wonder if reset_sctlr is really "sane values for a direct
kernel boot"?

> +
> +    /*
> +     * The Neoverse N2 has all of the Cortex-A710 IMPDEF registers,
> +     * and a few more RNG related ones.
> +     */
> +    define_arm_cp_regs(cpu, cortex_a710_cp_reginfo);
> +    define_arm_cp_regs(cpu, neoverse_n2_cp_reginfo);
> +
> +    aarch64_add_pauth_properties(obj);
> +    aarch64_add_sve_properties(obj);
> +}
> +
>  /*
>   * -cpu max: a CPU with as many features enabled as our emulation supports.
>   * The version of '-cpu max' for qemu-system-arm is defined in cpu32.c;
> @@ -1159,6 +1261,7 @@ static const ARMCPUInfo aarch64_cpus[] = {
>      { .name = "a64fx",              .initfn = aarch64_a64fx_initfn },
>      { .name = "neoverse-n1",        .initfn = aarch64_neoverse_n1_initfn },
>      { .name = "neoverse-v1",        .initfn = aarch64_neoverse_v1_initfn },
> +    { .name = "neoverse-n2",        .initfn = aarch64_neoverse_n2_initfn },
>  };
>  
>  static void aarch64_cpu_register_types(void)


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro