Re: [RFC PATCH v3 05/19] target/arm/kvm: enable writable implementation ID registers

> On 21 Jul 2026, at 8:33 PM, Eric Auger <[email protected]> wrote:
> 
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> Hi Khushit,
> 
> On 7/16/26 11:38 PM, Khushit Shah wrote:
>> Enable KVM_CAP_ARM_WRITABLE_IMP_ID_REGS if the host kernel supports it.
>> This allows QEMU to write implementation-defined ID registers (MIDR,
>> REVIDR) so that named CPU models can present the correct values to the
>> guest instead of inheriting the host's identity.
> This is a subset of 
> [RFC PATCH RESEND 0/4] hw/arm/virt: Add support for Target
> Implementation CPUs
> https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_all_20250801074730.28329-2D1-2Dshameerkolothum-40gmail.com_&d=DwIDaQ&c=s883GpUCOChKOHiocYtGcg&r=PGWMyignA0NiDmTlyP7vOTHozBws_VN86yrVmSMkBp0&m=pBBhKggpCKeDS4Sd7cXd8E5Cqhh-WjEbkh5Q-cSe_INp0NjOj69sFVBbwOAg7Pp1&s=Q-vKi5MLWdCzdKdXMUZ3wONnjAI6zV0Riawwl4UuVyo&e= 
> 
> and especially 1/4

Okay, interesting!  I will look into the series.

Warm Regards,
Khushit.
> 
> 
> Thanks
> 
> Eric
>> 
>> Signed-off-by: Khushit Shah <[email protected]>
>> ---
>> target/arm/kvm.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>> 
>> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
>> index 76583db3f0..63b3727e05 100644
>> --- a/target/arm/kvm.c
>> +++ b/target/arm/kvm.c
>> @@ -741,6 +741,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>>         }
>>     }
>> 
>> +    if (kvm_check_extension(s, KVM_CAP_ARM_WRITABLE_IMP_ID_REGS)) {
>> +        if (kvm_vm_enable_cap(s, KVM_CAP_ARM_WRITABLE_IMP_ID_REGS, 0)) {
>> +            error_report("Failed to enable "
>> +                         "KVM_CAP_ARM_WRITABLE_IMP_ID_REGS cap");
>> +        }
>> +    }
>> +
>>     if (s->kvm_eager_split_size) {
>>         uint32_t sizes;
>> 
>