Re: [PATCH 3/3] util/cpuinfo-riscv: Use linux __riscv_hwprobe syscall

[Richard Henderson <richard.henderson@linaro.org>]

On 7/2/24 15:15, Daniel Henrique Barboza wrote:
> 
> 
> On 6/27/24 3:03 PM, Richard Henderson wrote:
>> With recent linux kernels, there is a syscall to probe for various
>> ISA extensions.  These bits were phased in over several kernel
>> releases, so we still require checks for symbol availability.
>>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>   meson.build          |  6 ++++++
>>   util/cpuinfo-riscv.c | 26 ++++++++++++++++++++++++++
>>   2 files changed, 32 insertions(+)
>>
>> diff --git a/meson.build b/meson.build
>> index 97e00d6f59..58afd0125d 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -2837,6 +2837,12 @@ have_cpuid_h = cc.links('''
>>     }''')
>>   config_host_data.set('CONFIG_CPUID_H', have_cpuid_h)
>> +# Don't bother to advertise asm/hwprobe.h for old versions that do
>> +# not contain RISCV_HWPROBE_EXT_ZBA.
>> +config_host_data.set('CONFIG_ASM_HWPROBE_H',
>> +                     cc.has_header_symbol('asm/hwprobe.h',
>> +                                          'RISCV_HWPROBE_EXT_ZBA'))
>> +
> 
> FWIW I looked around Linux and I think we can snapshot hwprobe support by
> checking for RISCV_HWPROBE_KEY_IMA_EXT_0 (Linux commit 162e4df137c) if we
> ever need hwprobe for exts earlier than ZBA (C and V).

Sure.  It'll take some effort to use RVV for TCG vector operations.  :-)

> 
> Checking for ZBA is fine for this patch though.
> 
> 
> Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Thanks.


r~