RE: [PATCH v1 1/3] i386: Remove the limitation of IP payloads for Intel PT

[Kang, Luwei]

> >> No, it's not possible.  KVM doesn't have a say on what the processor
> >> writes in the tracing packets.
> > Can KVM refuse to enable packet generation if CSbase is not zero and
> > CPUID.(EAX=14H,ECX=0)[bit 31] seen by guest is different from host?
> 
> Yes, but the processor could change operating mode (and hence CSbase) while
> tracing is active.  This is very unlikely, since it would require nonzero 
> CS-base
> and a 32-bit host, but in principle not impossible (could be a firmware call, 
> for
> example).
> 
> The only solution is for KVM to accept both, and for QEMU to refuse a setting
> that does not match the host.
> 

So I need to add a patch in KVM to disabled the Intel PT when the CSbase is not 
zero and the guest LIP different from the host. And this limitation in qemu 
(disabled the PT when LIP is enabled in the host) can be remove. Is that right?

Thanks,
Luwei Kang