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Subject: Re: [PATCH 1/7] hyperv: Detect Nested virtualization support for SVM
To:     Sean Christopherson <seanjc@google.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "K. Y. Srinivasan" <kys@microsoft.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hyperv@vger.kernel.org,
        Lan Tianyu <Tianyu.Lan@microsoft.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, Wei Liu <wei.liu@kernel.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>
References: <cover.1617804573.git.viremana@linux.microsoft.com>
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 <87lf9tavci.fsf@vitty.brq.redhat.com>
 <af87c25e-78c6-5859-e1c1-2aa07d087a25@linux.microsoft.com>
 <YG8gPI6NZHGBc3Zl@google.com>
From:   Vineeth Pillai <viremana@linux.microsoft.com>
Message-ID: <cce1a04e-7b72-ea7f-d6eb-099a7e777cf3@linux.microsoft.com>
Date:   Fri, 9 Apr 2021 08:23:19 -0400
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On 4/8/21 11:24 AM, Sean Christopherson wrote:
>
> Technically, you can use normal memory accesses, so long as software guarantees
> the VMCS isn't resident in the VMCS cache and knows the field offsets for the
> underlying CPU.  The lack of an architecturally defined layout is the biggest
> issue, e.g. tacking on dirty bits through a PV ABI would be trivial.
>
>> Yes, you are right. I was referring to the fact that we cant use normal
>> memory accesses, but is a bit mis-worded.
> If you slot in "architectural" it will read nicely, i.e. "VMCB is already an
> architectural datastructure in memory".
Yes, this makes sense. Thanks for the suggestion, will reword as you
suggested.

Thanks,
Vineeth