> > CPUID(EAX=14H,ECX=0):EBX[bit 3] = 1 indicates support of output to > > Trace Transport subsystem. > > MSR IA32_RTIT_CTL.FabricEn[bit 6] is reserved if CPUID.(EAX=14H, > > ECX=0):ECX[bit 3] = 0. > > This should instead say: > > This adds support for "output to Trace Transport subsystem" capability of > Intel PT, as documented in IA SDM Chapter 36.x.y.z. It means that PT can > output its trace to an MMIO address range rather than system memory > buffer.
Yes, you are right. In KVM point of view this bit use for MSR access security check. KVM will track MSRs access in guest, an #GP will be injected to guest if guest try to write IA32_RTIT_CTL.FabricEn[bit 6] when "output_subsys" (CPUID.(EAX=14H, ECX=0):ECX[bit 3] = 0) is not supported. Thanks, Luwei Kang > > > This is use for emulate IA32_RTIT_CTL MSR read/write in KVM. KVM guest > > write IA32_RTIT_CTL will trap to root mode and a #GP would be injected > > to guest if set IA32_RTIT_CTL.FabricEn with CPUID.(EAX=14H, > > ECX=0):ECX[bit 3] = 0. > > I'm not sure what this means, this patch has nothing to do with KVM as far as > I can tell. > > Aside from the commit message, this is a valid patch. > > Thanks, > -- > Alex
