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

[Eduardo Habkost]

On Fri, Sep 25, 2020 at 10:23:49PM +0200, Paolo Bonzini wrote:
> On 25/09/20 18:54, Eduardo Habkost wrote:
> > On Fri, Sep 25, 2020 at 04:42:26PM +0000, Strong, Beeman wrote:
> >> LIP=0 will differ from LIP=1 behavior only when CSbase is non-zero, which 
> >> requires 32-bit code.  In that case a LIP=0 implementation will provide 
> >> only the EIP offset from CSbase in IP packets (like TIP or FUP), while 
> >> LIP=1 implementation will provide the full LIP (CSbase + EIP offset).
> >>
> > Thanks.  Is it possible to make KVM emulate LIP=0 behavior
> > correctly on LIP=1 hosts, or vice versa?
> 
> 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?

-- 
Eduardo