Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is enabled

[Paolo Bonzini]

On 21/08/20 11:22, Borislav Petkov wrote:
>> Hence the assumption that KVM makes (and has made ever since TSC_AUX was
>> introduced.
> And *this* is the problem. KVM can't just be grabbing MSRs and claiming
> them because it started using them first. You guys need to stop this. If
> it is a shared resource, there better be an agreement about sharing it.

It's not like we grab MSRs every day.  The user-return notifier restores
6 MSRs (7 on very old processors).  The last two that were added were
MSR_TSC_AUX itself in 2009 (!) and MSR_IA32_TSX_CTRL last year.

Paolo