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Date:   Thu, 22 Sep 2022 22:22:07 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     "Michael Kelley (LINUX)" <mikelley@microsoft.com>
Cc:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] x86/hyperv: Move VMCB enlightenment definitions to
 hyperv-tlfs.h
Message-ID: <YyzgD0xp/Ki9a3jK@google.com>
References: <20220921201607.3156750-1-seanjc@google.com>
 <20220921201607.3156750-2-seanjc@google.com>
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On Thu, Sep 22, 2022, Michael Kelley (LINUX) wrote:
> From: Sean Christopherson <seanjc@google.com> Sent: Wednesday, September 21, 2022 1:16 PM
> > 
> > Move Hyper-V's VMCB enlightenment definitions to the TLFS header; the
> > definitions come directly from the TLFS[*], not from KVM.
> > 
> > No functional change intended.
> > 
> > [*] https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/datatypes/hv_svm_enlightened_vmcb_fields> 
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > ---
> >  arch/x86/include/asm/hyperv-tlfs.h | 22 +++++++++++++++++++
> >  arch/x86/kvm/svm/hyperv.h          | 35 ------------------------------
> >  arch/x86/kvm/svm/svm_onhyperv.h    |  3 ++-
> >  3 files changed, 24 insertions(+), 36 deletions(-)
> >  delete mode 100644 arch/x86/kvm/svm/hyperv.h
> > 
> > diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> > index 0a9407dc0859..4c4f81daf5a2 100644
> > --- a/arch/x86/include/asm/hyperv-tlfs.h
> > +++ b/arch/x86/include/asm/hyperv-tlfs.h
> > @@ -584,6 +584,28 @@ struct hv_enlightened_vmcs {
> > 
> >  #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL			0xFFFF
> > 
> > +/*
> > + * Hyper-V uses the software reserved 32 bytes in VMCB control area to expose
> > + * SVM enlightenments to guests.
> > + */
> > +struct hv_enlightenments {
> > +	struct __packed hv_enlightenments_control {
> > +		u32 nested_flush_hypercall:1;
> > +		u32 msr_bitmap:1;
> > +		u32 enlightened_npt_tlb: 1;
> > +		u32 reserved:29;
> > +	} __packed hv_enlightenments_control;
> > +	u32 hv_vp_id;
> > +	u64 hv_vm_id;
> > +	u64 partition_assist_page;
> > +	u64 reserved;
> > +} __packed;
> > +
> > +/*
> > + * Hyper-V uses the software reserved clean bit in VMCB.
> > + */
> > +#define VMCB_HV_NESTED_ENLIGHTENMENTS		31
> 
> Is it feasible to change this identifier so it starts with HV_ like
> everything else in this source code file, such as
> HV_VMCB_NESTED_ENLIGHTENMENTS?  It doesn't look like it is
> used in very many places.  

Most definitely, IIRC it's used in only one spot.