Re: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write

[Thomas Gleixner]

Paolo Bonzini <pbonzini@xxxxxxxxxx> writes:
> On 03/02/20 16:16, Xiaoyao Li wrote:
>> A sane guest should never tigger emulation on a split-lock access, but
>> it cannot prevent malicous guest from doing this. So just emulating the
>> access as a write if it's a split-lock access to avoid malicous guest
>> polluting the kernel log.
>
> Saying that anything doing a split lock access is malicious makes little
> sense.

Correct, but we also have to accept, that split lock access can be used
in a malicious way, aka. DoS.

> Split lock detection is essentially a debugging feature, there's a
> reason why the MSR is called "TEST_CTL".  So you don't want to make the

The fact that it ended up in MSR_TEST_CTL does not say anything. That's
where they it ended up to be as it was hastily cobbled together for
whatever reason.

Thanks,

        tglx