Re: [patch V4 part 2 13/18] x86/kvm: Move context tracking where it belongs

[Thomas Gleixner]

Andy Lutomirski <luto@xxxxxxxxxx> writes:
> On Tue, May 5, 2020 at 7:14 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>>
>> Context tracking for KVM happens way too early in the vcpu_run()
>> code. Anything after guest_enter_irqoff() and before guest_exit_irqoff()
>> cannot use RCU and should also be not instrumented.
>>
>> The current way of doing this covers way too much code. Move it closer to
>> the actual vmenter/exit code.
>
> Now you've made me wonder what happens if someone traces
> vmx_vcpu_run().  I'm not sure I really want to think about this.

Been there, done that. Kinda worked but adding a kprobe into the guts of
it made it go sideways very fast.