On 20/11/2018 11:06, Jan Beulich wrote: >>>> On 15.11.18 at 22:47, <[email protected]> wrote: >> The final remnanat of PVRDTSCP is that we would emulate RDTSCP even on >> hardware which lacked the instruction. RDTSCP is available on almost all >> 64-bit x86 hardware. >> >> Remove this emulation, drop the TSC_MODE_PVRDTSCP constant, and allow RDTSCP >> in a PV guest's CPUID policy. > Why would we not want to emulate the insn when unavailable, when > it's generally useful to guests?
For exactly the same kind of safety reasons as for why we don't tolerate doing this in HVM guests in general. As it stands, it is an unnecessary attack surface, and if we were to re-introduce the functionality (not that I can see a valid reason to), it should use x86_emulate() rather than opencoding the logic. ~Andrew _______________________________________________ Xen-devel mailing list [email protected] https://lists.xenproject.org/mailman/listinfo/xen-devel
