linux-kernel - Re: [PATCH v7 4/7] KVM: VMX: Load Guest CET via VMCS when CET is enabled in Guest

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Date:   Thu, 10 Oct 2019 09:30:27 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH v7 4/7] KVM: VMX: Load Guest CET via VMCS when CET is
 enabled in Guest

On Wed, Oct 09, 2019 at 04:08:50PM -0700, Jim Mattson wrote:
> On Tue, Oct 8, 2019 at 11:41 PM Yang Weijiang <weijiang.yang@...el.com> wrote:
> >
> > On Wed, Oct 02, 2019 at 11:54:26AM -0700, Jim Mattson wrote:
> > > On Thu, Sep 26, 2019 at 7:17 PM Yang Weijiang <weijiang.yang@...el.com> wrote:
> > > > +       if (cet_on)
> > > > +               vmcs_set_bits(VM_ENTRY_CONTROLS,
> > > > +                             VM_ENTRY_LOAD_GUEST_CET_STATE);
> > >
> > > Have we ensured that this VM-entry control is supported on the platform?
> > >
> > If all the checks pass, is it enought to ensure the control bit supported?
> 
> I don't think so. The only way to check to see if a VM-entry control
> is supported is to check the relevant VMX capability MSR.
>
It's a bit odd, there's no relevant CET bit in VMX cap. MSR, so I have
to check like this.

> BTW, what about the corresponding VM-exit control?
The kernel supervisor mode CET is not implemented yet, so I don't load host CET
states on VM-exit, in future, I'll add it.