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Date:   Mon, 14 Sep 2020 14:37:08 -0700
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Tom Lendacky <thomas.lendacky@amd.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Brijesh Singh <brijesh.singh@amd.com>
Subject: Re: [RFC PATCH 25/35] KVM: x86: Update __get_sregs() / __set_sregs()
 to support SEV-ES
Message-ID: <20200914213708.GC7192@sjchrist-ice>
References: <cover.1600114548.git.thomas.lendacky@amd.com>
 <e08f56496a52a3a974310fbe05bb19100fd6c1d8.1600114548.git.thomas.lendacky@amd.com>
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On Mon, Sep 14, 2020 at 03:15:39PM -0500, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> Since many of the registers used by the SEV-ES are encrypted and cannot
> be read or written, adjust the __get_sregs() / __set_sregs() to only get
> or set the registers being tracked (efer, cr0, cr4 and cr8) once the VMSA
> is encrypted.

Is there an actual use case for writing said registers after the VMSA is
encrypted?  Assuming there's a separate "debug mode" and live migration has
special logic, can KVM simply reject the ioctl() if guest state is protected?