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From:   Jim Mattson <jmattson@google.com>
Date:   Thu, 13 Aug 2020 10:52:11 -0700
Message-ID: <CALMp9eQ5HhhXaEVKwnn6N6xxd2QOkNkE7ysiwq+3P=HB-Y1uzg@mail.gmail.com>
Subject: Re: [RFC 7/7] KVM: VMX: Enable PKS for nested VM
To:     Chenyi Qiang <chenyi.qiang@intel.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>,
        Xiaoyao Li <xiaoyao.li@intel.com>,
        kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Aug 12, 2020 at 9:54 PM Chenyi Qiang <chenyi.qiang@intel.com> wrote:
>
>
>
> On 8/11/2020 8:05 AM, Jim Mattson wrote:
> > On Fri, Aug 7, 2020 at 1:47 AM Chenyi Qiang <chenyi.qiang@intel.com> wrote:
> >>
> >> PKS MSR passes through guest directly. Configure the MSR to match the
> >> L0/L1 settings so that nested VM runs PKS properly.
> >>
> >> Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
> >> ---

> >> +           (!vmx->nested.nested_run_pending ||
> >> +            !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PKRS)))
> >> +               vmcs_write64(GUEST_IA32_PKRS, vmx->nested.vmcs01_guest_pkrs);
> >
> > This doesn't seem right to me. On the target of a live migration, with
> > L2 active at the time the snapshot was taken (i.e.,
> > vmx->nested.nested_run_pending=0), it looks like we're going to try to
> > overwrite the current L2 PKRS value with L1's PKRS value (except that
> > in this situation, vmx->nested.vmcs01_guest_pkrs should actually be
> > 0). Am I missing something?
> >
>
> We overwrite the L2 PKRS with L1's value when L2 doesn't support PKS.
> Because the L1's VM_ENTRY_LOAD_IA32_PKRS is off, we need to migrate L1's
> PKRS to L2.

I'm thinking of the case where vmx->nested.nested_run_pending is
false, and we are processing a KVM_SET_NESTED_STATE ioctl, yet
VM_ENTRY_LOAD_IA32_PKRS *is* set in the vmcs12.