----- sean.j.christopherson@xxxxxxxxx wrote:
> On Tue, 2018-05-22 at 08:50 -0700, Jim Mattson wrote:
> > While we're on the subject, is there any need for L0 to allocate a
> > vpid02 in the common case, where nested EPT is enabled?
> >
> > Per section 28.3.2 of the SDM, volume 3, when EPT is enabled,
> combined
> > mappings in the TLB are tagged by {VPID, PCID, EP4TA}. With nested
> > EPT, vmcs02 and vmcs01 do not share an EP4TA. Therefore, I think it
> > suffices to simply copy the VPID field from vmcs12 to vmcs02 in
> this
> > case.
>
> VPID handling in general looks like it could use a good once-over,
> e.g. vpid02 allocation can be delayed until prepare_vmcs02_full(),
> we never re-attempt VPID allocation in the (extremely unlikely)
> case that there are no available VPIDs at vmx_create_vcpu(), and
> load_vmcs12_host_state() explicitly flushes the TLB when VPID is
> enabled because it has obsolete code that assumes L1 and L2 always
> share a VPID.
Agree with all the above.
As a starting point, I think we should apply this current series as it at-least
handle the load_vmcs12_host_state() issue. :)
Will also add handling for the rest of these issues in my upcoming series.
Thanks for explicitly pointing these out.
>
> > On Tue, May 22, 2018 at 7:16 AM, Liran Alon <liran.alon@xxxxxxxxxx>
> wrote:
> > >
> > > Hi,
> > >
> > > This series aims to optimize KVM nested-VPID implementation.
> > > Note: All the patches in this series are indepdendent and can be
> > > applied seperately.
> > >
> > > 1st patch is just a small refactoring change.
> > >
> > > 2nd patch fixes a corner-case of not failing INVVPID type 0
> > > (individiual-address) in case operand.vpid==0.
> > >
> > > 3rd patch fixes an ancient issue of unnecessarely flushing TLB
> when
> > > exiting from L2 to L1 even though TLB entries populated by L2 are
> > > tagged with different VPID (vmx->nested.vpid02) than TLB entries
> > > populated by L1 (vmx->vpid).
> > >
> > > 4rd patch optimizes L1 INVVPID type 0 (individiual-address)
> handling
> > > by emulating it with INVVPID type 0 executed at L0 level. This
> allows
> > > flushing only a single TLB entry tagged with vmx->nested.vpid02
> > > instead of all TLB entries tagged with vmx->nested.vpid02.
> > >
> > > Regards,
> > > -Liran Alon
