From: Tobin Feldman-Fitzthum <tobin@linux.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.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>
Subject: Re: [RFC] KVM: x86: Support KVM VMs sharing SEV context
Date: Mon, 15 Mar 2021 13:05:16 -0400 [thread overview]
Message-ID: <adb84c91-1651-94b6-0084-f86296e96530@linux.ibm.com> (raw)
In-Reply-To: <35dde628-f1a8-c3bf-9c7d-7789166b0ee1@redhat.com>
On 3/11/21 11:29 AM, Paolo Bonzini wrote:
> On 11/03/21 16:30, Tobin Feldman-Fitzthum wrote:
>> I am not sure how the mirror VM will be supported in QEMU. Usually
>> there is one QEMU process per-vm. Now we would need to run a second
>> VM and communicate with it during migration. Is there a way to do
>> this without adding significant complexity?
>
> 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.
-Tobin
>
> I also think (but I'm not 100% sure) that the auxiliary VM does not
> have to watch changes in the primary VM's memory map (e.g. mapping and
> unmapping of BARs). In QEMU terms, the auxiliary VM's memory map
> tracks RAMBlocks, not MemoryRegions, which makes things much simpler.
>
> There are already many examples of mini VMMs running special purpose
> VMs in the kernel's tools/testing/selftests/kvm directory, and I don't
> think the QEMU code would be any more complex than that.
>
> Paolo
>
next prev parent reply other threads:[~2021-03-15 17:06 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-24 8:59 [RFC] KVM: x86: Support KVM VMs sharing SEV context Nathan Tempelman
2021-02-24 9:18 ` Paolo Bonzini
2021-02-24 16:58 ` Sean Christopherson
2021-02-25 11:26 ` Paolo Bonzini
2021-02-24 17:37 ` Sean Christopherson
2021-02-25 3:55 ` Steve Rutherford
2021-03-12 23:47 ` Nathan Tempelman
2021-03-16 17:52 ` Sean Christopherson
2021-03-16 17:58 ` Paolo Bonzini
2021-03-16 18:08 ` Sean Christopherson
2021-02-25 3:44 ` Steve Rutherford
2021-02-25 14:57 ` Tom Lendacky
2021-02-25 18:49 ` Steve Rutherford
2021-03-05 22:36 ` Ashish Kalra
2021-03-09 17:45 ` Sean Christopherson
2021-02-25 17:53 ` James Bottomley
2021-02-25 18:18 ` Ashish Kalra
2021-02-25 20:33 ` Paolo Bonzini
2021-02-26 13:30 ` Ashish Kalra
2021-02-25 20:36 ` Paolo Bonzini
2021-03-05 14:04 ` Ashish Kalra
2021-03-05 15:13 ` Paolo Bonzini
2021-03-05 20:43 ` Nathan Tempelman
2021-03-11 15:30 ` Tobin Feldman-Fitzthum
2021-03-11 16:29 ` Paolo Bonzini
2021-03-15 17:05 ` Tobin Feldman-Fitzthum [this message]
2021-03-15 17:29 ` Paolo Bonzini
2021-05-24 21:29 ` Kalra, Ashish
2021-05-27 15:51 ` Kalra, Ashish
2021-06-01 8:26 ` Kalra, Ashish
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