Re: [PATCH 1/7] hyperv: Detect Nested virtualization support for SVM

From: Vineeth Pillai <viremana@linux.microsoft.com>
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>
Subject: Re: [PATCH 1/7] hyperv: Detect Nested virtualization support for SVM
Date: Fri, 9 Apr 2021 08:23:19 -0400	[thread overview]
Message-ID: <cce1a04e-7b72-ea7f-d6eb-099a7e777cf3@linux.microsoft.com> (raw)
In-Reply-To: <YG8gPI6NZHGBc3Zl@google.com>


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