Re: [PATCH 03/16] target/riscv/cpu.c: restrict 'mvendorid' value

From: Andrew Jones <ajones@ventanamicro.com>
To: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Cc: qemu-devel@nongnu.org, qemu-riscv@nongnu.org,
	alistair.francis@wdc.com,  bmeng@tinylab.org,
	liweiwei@iscas.ac.cn, zhiwei_liu@linux.alibaba.com,
	 palmer@rivosinc.com
Subject: Re: [PATCH 03/16] target/riscv/cpu.c: restrict 'mvendorid' value
Date: Tue, 6 Jun 2023 15:19:06 +0200	[thread overview]
Message-ID: <20230606-aadc97a378f5d52fd233dcaa@orel> (raw)
In-Reply-To: <20230530194623.272652-4-dbarboza@ventanamicro.com>

On Tue, May 30, 2023 at 04:46:10PM -0300, Daniel Henrique Barboza wrote:
> We're going to change the handling of mvendorid/marchid/mimpid by the
> KVM driver. Since these are always present in all CPUs let's put the
> same validation for everyone.
> 
> It doesn't make sense to allow 'mvendorid' to be different than it
> is already set in named (vendor) CPUs. Generic (dynamic) CPUs can have
> any 'mvendorid' they want.
> 
> Change 'mvendorid' to be a class property created via
> 'object_class_property_add', instead of using the DEFINE_PROP_UINT32()
> macro. This allow us to define a custom setter for it that will verify,
> for named CPUs, if mvendorid is different than it is already set by the
> CPU. This is the error thrown for the 'veyron-v1' CPU if 'mvendorid' is
> set to an invalid value:
> 
> $ qemu-system-riscv64 -M virt -nographic -cpu veyron-v1,mvendorid=2
> qemu-system-riscv64: can't apply global veyron-v1-riscv-cpu.mvendorid=2:
>     Unable to change veyron-v1-riscv-cpu mvendorid (0x61f)
> 
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  target/riscv/cpu.c | 31 ++++++++++++++++++++++++++++++-
>  1 file changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 72f5433776..bcd69bb032 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1723,7 +1723,6 @@ static void riscv_cpu_add_user_properties(Object *obj)
>  static Property riscv_cpu_properties[] = {
>      DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
>  
> -    DEFINE_PROP_UINT32("mvendorid", RISCVCPU, cfg.mvendorid, 0),
>      DEFINE_PROP_UINT64("marchid", RISCVCPU, cfg.marchid, RISCV_CPU_MARCHID),
>      DEFINE_PROP_UINT64("mimpid", RISCVCPU, cfg.mimpid, RISCV_CPU_MIMPID),
>  
> @@ -1810,6 +1809,32 @@ static const struct TCGCPUOps riscv_tcg_ops = {
>  #endif /* !CONFIG_USER_ONLY */
>  };
>  
> +static bool riscv_cpu_is_dynamic(Object *cpu_obj)
> +{
> +    return object_dynamic_cast(cpu_obj, TYPE_RISCV_DYNAMIC_CPU) != NULL;
> +}
> +
> +static void cpu_set_mvendorid(Object *obj, Visitor *v, const char *name,
> +                              void *opaque, Error **errp)
> +{
> +    bool dynamic_cpu = riscv_cpu_is_dynamic(obj);
> +    RISCVCPU *cpu = RISCV_CPU(obj);
> +    uint32_t prev_val = cpu->cfg.mvendorid;
> +    uint32_t value;
> +
> +    if (!visit_type_uint32(v, name, &value, errp)) {
> +        return;
> +    }
> +
> +    if (!dynamic_cpu && prev_val != value) {
> +        error_setg(errp, "Unable to change %s mvendorid (0x%x)",
> +                   object_get_typename(obj), prev_val);
> +        return;
> +    }
> +
> +    cpu->cfg.mvendorid = value;
> +}
> +
>  static void riscv_cpu_class_init(ObjectClass *c, void *data)
>  {
>      RISCVCPUClass *mcc = RISCV_CPU_CLASS(c);
> @@ -1841,6 +1866,10 @@ static void riscv_cpu_class_init(ObjectClass *c, void *data)
>      cc->gdb_get_dynamic_xml = riscv_gdb_get_dynamic_xml;
>      cc->tcg_ops = &riscv_tcg_ops;
>  
> +    object_class_property_add(c, "mvendorid", "uint32", NULL,
> +                              cpu_set_mvendorid,
> +                              NULL, NULL);
> +

Shouldn't we provide a get function as well?

>      device_class_set_props(dc, riscv_cpu_properties);
>  }
>  
> -- 
> 2.40.1
> 
> 

Otherwise,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>