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Subject: Re: [RFC] KVM: x86: Support KVM VMs sharing SEV context
To:     Tobin Feldman-Fitzthum <tobin@linux.ibm.com>, natet@google.com
Cc:     Dov Murik <dovmurik@linux.vnet.ibm.com>,
        Tom Lendacky <thomas.lendacky@amd.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        srutherford@google.com, seanjc@google.com, rientjes@google.com,
        Brijesh Singh <brijesh.singh@amd.com>,
        Ashish Kalra <ashish.kalra@amd.com>,
        Laszlo Ersek <lersek@redhat.com>,
        James Bottomley <jejb@linux.ibm.com>,
        Hubertus Franke <frankeh@us.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>
References: <20210224085915.28751-1-natet@google.com>
 <7829472d-741c-1057-c61f-321fcfb5bdcd@linux.ibm.com>
 <35dde628-f1a8-c3bf-9c7d-7789166b0ee1@redhat.com>
 <adb84c91-1651-94b6-0084-f86296e96530@linux.ibm.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <69004ca1-93a7-6a7e-b349-05f857756334@redhat.com>
Date:   Mon, 15 Mar 2021 18:29:59 +0100
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On 15/03/21 18:05, Tobin Feldman-Fitzthum wrote:
>>
>> I can answer this part.  I think this will actually be simpler than 
>> with auxiliary vCPUs.  There will be a separate pair of VM+vCPU file 
>> descriptors within the same QEMU process, and some code to set up the 
>> memory map using KVM_SET_USER_MEMORY_REGION.
>>
>> However, the code to run this VM will be very small as the VM does not 
>> have to do MMIO, interrupts, live migration (of itself), etc.  It just 
>> starts up and communicates with QEMU using a mailbox at a 
>> predetermined address.
> 
> We've been starting up our Migration Handler via OVMF. I'm not sure if 
> this would work with a minimal setup in QEMU.

Yeah, the way to start up the migration handler would be completely 
different, you'd have to do so very early (probably SEC).

Paolo