Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 4 Sep 2019 21:49:25 +0800
From:   Yang Weijiang <weijiang.yang@intel.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Yang Weijiang <weijiang.yang@intel.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com,
        mst@redhat.com, rkrcmar@redhat.com, jmattson@google.com,
        yu.c.zhang@intel.com, alazar@bitdefender.com
Subject: Re: [PATCH RESEND v4 8/9] KVM: MMU: Enable Lazy mode SPPT setup
Message-ID: <20190904134925.GA25149@local-michael-cet-test.sh.intel.com>
References: <20190814070403.6588-1-weijiang.yang@intel.com>
 <20190814070403.6588-9-weijiang.yang@intel.com>
 <63f8952b-2497-16ec-ff55-1da017c50a8c@redhat.com>
 <20190820131214.GD4828@local-michael-cet-test.sh.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190820131214.GD4828@local-michael-cet-test.sh.intel.com>
User-Agent: Mutt/1.11.3 (2019-02-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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!