https://bugzilla.kernel.org/show_bug.cgi?id=54161 Summary: nVMX: nested vpid Product: Virtualization Version: unspecified Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: enhancement Priority: P1 Component: kvm AssignedTo: virtualization_kvm@xxxxxxxxxxxxxxxxxxxx ReportedBy: nyh@xxxxxxxxxxxxxxxxxxx Regression: No Currently, support for VPID in nested VMX is minimal: L1 doesn't see the vpid feature, and doesn't use it, but L0 may use it (if available) when running the guests: We use the same vpid to run L1 and all its L2 guests, but vmx_flush_tlb(vcpu) when going back and forth between L1 and L2 - this flushes this particular vpid, but at least leave other L1's cache entries behind. A better performing solution would be to support "nested vpid" - L0 exposes to L1 the VPID feature, and maintains a mapping between VPID numbers that L1 uses to VPID numbers that it uses. L0 runs each of its guests - L1s and L2s, as separate guests. Some points to remember while doing this (this is only a partial list!): 1. Remember to set vmx->vpid on nested_vmx_run() and nested_vmx_vmexit() to L1's and L2's vpid. This is important because vmx_flush_tlb() (called on context switch between a guest's processes) flushes only the current vpid (if possible) and we need to do it to the correct one. 2. In free_nested(), also free the vpids that have been allocated to all the L2s. This can probably be done in nested_free_saved_vmcs() (see mention above). However, note that free_nested() is preceded (in vmx_free_vcpu()) by a call to free_vpid() which frees the current vmx->vpid, which might be l1 or l2 and we need to make sure we free all of them, and just once. 3. Implement, of course, also INVVPID for L1. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug. -- 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
