Re: [PATCH RESEND v4 8/9] KVM: MMU: Enable Lazy mode SPPT setup

Yang Weijiang
2019-09-04T13:48:31Z

On Tue, Aug 20, 2019 at 09:12:14PM +0800, Yang Weijiang wrote:
> On Mon, Aug 19, 2019 at 04:46:54PM +0200, Paolo Bonzini wrote:
> > On 14/08/19 09:04, Yang Weijiang wrote:
> > > +
> > > + if (vcpu->kvm->arch.spp_active && level == PT_PAGE_TABLE_LEVEL)
> > > + kvm_enable_spp_protection(vcpu->kvm, gfn);
> > > +
> >
> > This would not enable SPP if the guest is backed by huge pages.
> > Instead, either the PT_PAGE_TABLE_LEVEL level must be forced for all
> > pages covered by SPP ranges, or (better) kvm_enable_spp_protection must
> > be able to cover multiple pages at once.
> >
> > Paolo
> OK, I'll figure out how to make it, thanks!
Hi, Paolo,
Regarding this change, I have some concerns, splitting EPT huge page
entries(e.g., 1GB page)will take long time compared with normal EPT page
fault processing, especially for multiple vcpus/pages,so the in-flight time increases,
but HW walks EPT for translations in the meantime, would it bring any side effect?
or there's a way to mitigate it?

Thanks!