On 17.09.2019 21:59, Andrew Cooper wrote: > On 17/09/2019 07:17, Jan Beulich wrote: >> PCID validly depends on LM, as it can be enabled in Long Mode only. >> INVPCID, otoh, can be used not only without PCID enabled, but also >> outside of Long Mode altogether. In both cases its functionality is >> simply restricted to PCID 0, which is sort of expected as no other PCID >> can be activated there. >> >> Signed-off-by: Jan Beulich <jbeul...@suse.com> >> Reviewed-by: Roger Pau Monné <roger....@citrix.com> >> >> --- a/xen/tools/gen-cpuid.py >> +++ b/xen/tools/gen-cpuid.py >> @@ -218,10 +218,6 @@ def crunch_numbers(state): >> # >> # SSE4_2: [POPCNT] >> >> - # The INVPCID instruction depends on PCID infrastructure being >> - # available. >> - PCID: [INVPCID], > > I take it you haven't tried running a shadow guest with this change in > place. > > For !EPT, we clear ENABLE_INVPCID so the instruction will #UD within the > guest. > > We could in principle allow the use of INVPCID with shadow guests, but > that would involve teaching Xen how to cope with VMEXIT_REASON_INVPCID > (which is predicated on INVLPG exiting) and wire the flush back into the > shadow logic. > > Perhaps the comment could be a little clearer, but it is no accident > that dependency is in place.
I'm afraid I don't follow: Both features are marked H in the public header, so I don't see how shadow mode considerations apply here at all. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel