linux-kernel - Re: [PATCH v2 1/7] KVM:VMX: Define CET VMCS fields and bits

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Date:   Tue, 29 Jan 2019 16:34:28 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>, yu-cheng.yu@...el.com,
        yi.z.zhang@...el.com, hjl.tools@...il.com,
        Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v2 1/7] KVM:VMX: Define CET VMCS fields and bits

On Tue, Jan 29, 2019 at 10:27:50AM -0800, Sean Christopherson wrote:
> On Tue, Jan 29, 2019 at 10:01:15AM -0800, Jim Mattson wrote:
> > On Tue, Jan 29, 2019 at 9:47 AM Jim Mattson <jmattson@...gle.com> wrote:
> > >
> > > On Wed, Jan 23, 2019 at 6:06 AM Yang Weijiang <weijiang.yang@...el.com> wrote:
> > > > Note: Although these VMCS fields are 64-bit, they don't have high fields.
> > >
> > > This statement directly contradicts the SDM, volume 3, appendix B.2:
> > >
> > > "A value of 1 in bits 14:13 of an encoding indicates a 64-bit field.
> > > There are 64-bit fields only for controls and for guest state. As
> > > noted in Section 24.11.2, every 64-bit field has two encodings, which
> > > differ on bit 0, the access type. Thus, each such field has an even
> > > encoding for full access and an odd encoding for high access."
> > 
> > Ah! They're not actually 64-bit fields. If you look at the encodings
> > (0x68XX and 0x6cxx), they're natural-width fields! Natural-width
> > fields don't have a high component.
> 
> They're indeed natural width (I actually looked at the spec this time).
> 
> The "_FULL" postfix on VMX_HOST_IA32_INTERRUPT_SSP_TABLE_ADDR_FULL and
> VMX_HOST_SSP_FULL is confusing as it generally only shows up on 64-bit
> fields.  I'll see if we can get the fields renamed to drop "_FULL".  I
> suggest we preemptively do the same for KVM.
Thank you for making it clear! I should have modified the annotation
correctly. I'll add a note for this in next version.