Re: [PATCH 4/5] hw/arm/virt: Add FW_CFG_RAM_SIZE and FW_CFG_MAX_CPUS into fw_cfg

[Xiang Zheng <zhengxiang9@huawei.com>]

On 2019/12/3 20:32, Peter Maydell wrote:
> On Tue, 3 Dec 2019 at 12:29, Xiang Zheng <zhengxiang9@huawei.com> wrote:
>>
>> I'm not sure whether it's neccesary to add FW_CFG_RAM_SIZE and
>> FW_CFG_MAX_CPUS into fw_cfg on virt machine. This patch just makes
>> the fw_cfg-test happy.
>>
>> Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com>
>> ---
>>  hw/arm/virt.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index d4bedc2607..26a4183775 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -1084,6 +1084,9 @@ static FWCfgState *create_fw_cfg(const VirtMachineState *vms, AddressSpace *as)
>>      fw_cfg = fw_cfg_init_mem_wide(base + 8, base, 8, base + 16, as);
>>      fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, (uint16_t)ms->smp.cpus);
>>
>> +    fw_cfg_add_i64(fw_cfg, FW_CFG_RAM_SIZE, (uint64_t)ram_size);
>> +    fw_cfg_add_i16(fw_cfg, FW_CFG_MAX_CPUS, (uint16_t)ms->smp.max_cpus);
>> +
>>      nodename = g_strdup_printf("/fw-cfg@%" PRIx64, base);
>>      qemu_fdt_add_subnode(vms->fdt, nodename);
>>      qemu_fdt_setprop_string(vms->fdt, nodename,
>> --
> 
> Is there a spec anywhere that defines the meaning of these
> FW_CFG entries ? docs/specs/fw_cfg.txt defines the
> device interface but not what the 'standard' keys mean.
> I'd prefer not to add them to the virt board without knowing
> what they mean and why we have them.
> 

I cannot find a spec or doc defines these FW_CFG entries. It seems that they
are used on x86 machines to limit APIC ID values but useless on virt machine.
I will drop this patch.

-- 

Thanks,
Xiang