On 26/01/2021 14:27, Jan Beulich wrote: > On 21.01.2021 22:27, Andrew Cooper wrote: >> --- a/xen/arch/x86/vm_event.c >> +++ b/xen/arch/x86/vm_event.c >> @@ -251,6 +251,9 @@ void vm_event_fill_regs(vm_event_request_t *req) >> >> req->data.regs.x86.shadow_gs = ctxt.shadow_gs; >> req->data.regs.x86.dr6 = ctxt.dr6; >> + >> + if ( hvm_vmtrace_output_position(curr, &req->data.regs.x86.pt_offset) >> != 1 ) >> + req->data.regs.x86.pt_offset = ~0; > Ah. (Regarding my earlier question about this returning -errno or > boolean). > >> --- a/xen/include/public/vm_event.h >> +++ b/xen/include/public/vm_event.h >> @@ -223,6 +223,12 @@ struct vm_event_regs_x86 { >> */ >> uint64_t npt_base; >> >> + /* >> + * Current offset in the Processor Trace buffer. For Intel Processor >> Trace >> + * this is MSR_RTIT_OUTPUT_MASK. Set to ~0 if no Processor Trace is >> active. >> + */ >> + uint64_t pt_offset; > According to vmtrace_output_position() the value is only one half > of what the named MSR contains. Perhaps "... this is from MSR_..."? > Not sure whether, despite this, there still is a reason to have > this 64-bit wide.
This is a vestigial remnant which escaped the "use vmtrace uniformly" work. It should match the domctl_vmtrace_output_position() format, so each interface gives the same content for the attempted-platform-neutral version. ~Andrew