On 2/7/26 9:44 PM, Paolo Bonzini wrote:
>
>
> On 1/9/26 03:10, Ewan Hai wrote:
>> Update the comment for FEAT_C000_0001_EDX in YongFeng CPU model to
>> accurately list the missing features instead of the generic TODO message.
>>
>> As background, current Zhaoxin CPUs implement several CPUID.(EAX=0xC0000001,
>> ECX=0):EDX feature bits that are not yet defined in the Linux kernel, for
>> example SM2/SM2_EN, SM3/SM4 and their enable bits, PARALLAX/PARALLAX_EN,
>> TM3/TM3_EN, RNG2/RNG2_EN, PHE2/PHE2_EN, and RSA/RSA_EN.
>>
>> We previously tried to upstream all these extra feature bits in one patch
>> (https://lore.kernel.org/all/[email protected]/),
>> but the maintainer rejected it because there was no in-tree code using these
>> features yet. So our current plan is to add the CPUID bits together with real
>> kernel users step by step, Once full or partial in-tree implementations of
>> these features are merged, we will update these definitions accordingly and
>> potentially introduce corresponding support in QEMU.
>
> KVM now has a mechanism for introducing feature bits separately from the
> kernel. Feel free to resumit using that mechanism, then we can include
> them from the beginning in Shinjidadao.
>
> Thanks,
>
> Paolo
Hi Paolo,
Thanks for pointing out that KVM has a mechanism for introducing feature bits
independently from the kernel.
Before I start working on the patches, I'd like to clarify a few things:
1. Which specific mechanism are you referring to?
a) The kvm_only_cpuid_leafs enum + kvm_cpu_cap_init_kvm_defined()?
b) Or some other approach, given that CPUID_C000_0001_EDX is already
a kernel-defined leaf (word 5)?
2. Should this independent introduction be limited to CPUID_C000_0001_EDX only
For other feature words, I assume they still need to be handled on a
case-by-case basis depending on their semantics and QEMU support status,
correct?
For context: I want to add SM2/SM3/SM4/RNG2/PHE2/RSA etc. bits to
0xC0000001.EDX, but these features don't have in-tree kernel users yet.
Thanks,
Ewan
>> Signed-off-by: Ewan Hai <[email protected]>
>> ---
>> target/i386/cpu.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index 34e3e66344..10603eeb31 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -6958,8 +6958,8 @@ static const X86CPUDefinition builtin_x86_defs[] = {
>> CPUID_EXT3_3DNOWPREFETCH | CPUID_EXT3_ABM | CPUID_EXT3_LAHF_LM,
>> .features[FEAT_8000_0007_EDX] = CPUID_APM_INVTSC,
>> /*
>> - * TODO: When the Linux kernel introduces other existing definitions
>> - * for this leaf, remember to update the definitions here.
>> + * missing: SM2/SM2_EN, CCS/CCS_EN, PARALLAX/PARALLAX_EN,
>> + * TM3/TM3_EN, RNG2/RNG2_EN, PHE2/PHE2_EN, RSA/RSA_EN
>> */
>> .features[FEAT_C000_0001_EDX] =
>> CPUID_C000_0001_EDX_PMM_EN | CPUID_C000_0001_EDX_PMM |
>
