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

[Paolo Bonzini]

On 25/09/20 22:29, Eduardo Habkost wrote:
>> 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.

Paolo