On 26/02/18 11:25, Jan Beulich wrote: >>>> On 20.02.18 at 12:58, <andrew.coop...@citrix.com> 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. >> >> At the moment, paravirt_ctxt_switch_to() only writes to MSR_TSC_AUX if >> TSC_MODE_PVRDTSCP mode is enabled, but this is not the default mode. >> Therefore, default PV guests can read the value from a previously scheduled >> HVM vcpu, or TSC_MODE_PVRDTSCP-enabled PV guest. >> >> Alter the PV path to always write to MSR_TSC_AUX, using 0 in the common >> case. >> >> To amortise overhead cost, introduce wrmsr_tsc_aux() which performs a lazy >> update of the MSR, and use this function consistently across the codebase. >> >> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com> > Despite me continuing to think that RDTSCP and RDPID should be > fully independent features, this being in line with the SDM: > Acked-by: Jan Beulich <jbeul...@suse.com>
Thanks. Given the important of this patch, I feel it is time to ping the VT-x and SVM maintainers for their input. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel