On Mon, May 14, 2012 at 07:15:18AM +0000, Mao, Junjie wrote: > > On Wed, May 9, 2012 at 5:32 PM, Mao, Junjie <junjie.mao@xxxxxxxxx> wrote: > > > This patch handles PCID/INVPCID for guests. > > > > > > Process-context identifiers (PCIDs) are a facility by which a logical processor may cache information for multiple linear-address spaces so that the processor may retain cached information when software switches to a different linear-address space. Refer to section 4.10.1 in IA32 Intel Software Developer's Manual Volume 3A for details. > > > > > > For guests with EPT, the PCID feature is enabled and INVPCID behaves as running natively. > > > For guests without EPT, the PCID feature is disabled and INVPCID triggers #UD. > > > > > Do I understand correctly that this means it is impossible to migrate a guest which is using PCID from a host with EPT to a host without EPT (by passing enable_ept=0 to the module, for example) ? > > I think you are right. Guests using PCID/INVPCID cannot migrate to a host without it, and EPT is a precondition of this feature. Are there processors that support PCI/INVPCID for the host but lack support for SECONDARY_EXEC_ENABLE_INVPCID? > > Does the emulated CR3 load need to learn about the new function of the low bits? > > I have not found any restrictions on writing CR3 brings about by PCID. It would be good for completeness. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
