Jan Kiszka <jan.kiszka@xxxxxxxxxxx> writes: > On 2014-04-11 02:27, Bandan Das wrote: >> Marcelo Tosatti <mtosatti@xxxxxxxxxx> writes: >> >>> On Mon, Mar 31, 2014 at 05:00:23PM -0400, Bandan Das wrote: >>>> For single context invalidation, we fall through to global >>>> invalidation in handle_invept() except for one case - when >>>> the operand supplied by L1 is different from what we have in >>>> vmcs12. However, typically hypervisors will only call invept >>>> for the currently loaded eptp, so the condition will >>>> never be true. >>>> >>>> Signed-off-by: Bandan Das <bsd@xxxxxxxxxx> >>> >>> Bandan, >>> >>> Why not fix INVEPT single-context rather than removing it entirely? >>> >>> "Single-context. If the INVEPT type is 1, the logical processor >>> invalidates all guest-physical mappings and combined mappings associated >>> with the EP4TA specified in the INVEPT descriptor. Combined mappings for >>> that EP4TA are invalidated for all VPIDs and all PCIDs. (The instruction >>> may invalidate mappings associated with other EP4TAs.)" >>> >>> So just removing the "if (EPTP != CURRENT.EPTP) BREAK" should be enough. >> >> The single context invalidation in handle_invept() doesn't do >> anything different. It just falls down to the global case. >> And the invept code in Xen and KVM both seemed to fall back >> to global invalidation if support for single context wasn't found. >> So, it was proposed not to advertise it at all. >> >> But rethinking this again, I agree with you. If there's a hypervisor >> with a single context invept implmentation that does not fallback, >> this will unfortunately not work. Jan, do you agree with this ? > > A hypervisor that doesn't properly check the HW caps is just broken. And > one that mandates single context invalidation support is silly. Well, but we could make life a little bit easier for the unfortunate user using the broken hypervisor :) And advertising single context inavalidation doesn't really seem to have any downsides. > Jan -- 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
