On Tue, Feb 20, 2018 at 03:26:20PM +0000, Andrew Cooper wrote: > On 20/02/18 15:22, Wei Liu wrote: > > On Tue, Feb 20, 2018 at 11:58:40AM +0000, Andrew Cooper wrote: > >> If the CPU pipeline supports RDTSCP or RDPID, a guest can observe the > >> value in > >> MSR_TSC_AUX, irrespective of whether the relevant CPUID features are > >> advertised/hidden. > >> > > This setup works only because CR4.TSD=0? > > Having CR4.TSD clear is the default, and means RDTSCP will work at any > privilege level. Setting CR4.TSD (either due to virtualised TSC, or > because the guest kernel wants to trap user accesses) will cause RDTSCP > to trap into emul-priv-op. > > There is no way of causing RDPID to trap (on hardware which supports the > instruction), and it will read read the current value of MSR_TSC_AUX.
Alright. In any case: Reviewed-by: Wei Liu <wei.l...@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
