Re: [PATCH] i386/cpu: ARCH_CAPABILITIES should not be advertised on AMD

[Alexandre Chartre <alexandre.chartre@oracle.com>]

On 7/1/25 13:12, Xiaoyao Li wrote:
> On 7/1/2025 6:26 PM, Zhao Liu wrote:
>>> unless it was explicitly requested by the user.
>> But this could still break Windows, just like issue #3001, which enables
>> arch-capabilities for EPYC-Genoa. This fact shows that even explicitly
>> turning on arch-capabilities in AMD Guest and utilizing KVM's emulated
>> value would even break something.
>>
>> So even for named CPUs, arch-capabilities=on doesn't reflect the fact
>> that it is purely emulated, and is (maybe?) harmful.
> 
> It is because Windows adds wrong code. So it breaks itself and it's just the regression of Windows.
> 
> KVM and QEMU are not supposed to be blamed.

I can understand the Windows code logic, and I don't think it is necessarily wrong,
because it finds that the system has:

- an AMD cpu
- an Intel-only feature/MSR

Then what should the code do? Trust the cpu type (AMD) or trust the MSR (Intel).
They decided not to choose, and for safety they stop because they have an unexpected
configuration.

alex.