On 28/09/20 07:19, Kang, Luwei 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. >> > > 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?
No, if a feature cannot be emulated, that means it cannot be enabled unless it matches the host. That's generally not a problem since Intel PT is usually used only with "-cpu host". Paolo
