Re: [RFC PATCH 00/13] Add support for Mirror VM.

[Claudio Fontana]

On 8/16/21 3:25 PM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
> 
> This is an RFC series for Mirror VM support that are 
> essentially secondary VMs sharing the encryption context 
> (ASID) with a primary VM. The patch-set creates a new 
> VM and shares the primary VM's encryption context
> with it using the KVM_CAP_VM_COPY_ENC_CONTEXT_FROM capability.
> The mirror VM uses a separate pair of VM + vCPU file 
> descriptors and also uses a simplified KVM run loop, 
> for example, it does not support any interrupt vmexit's. etc.
> Currently the mirror VM shares the address space of the
> primary VM. 

Hi,

I'd expect some entry in docs/ ?

Thanks,

Claudio

> 
> The mirror VM can be used for running an in-guest migration 
> helper (MH). It also might have future uses for other in-guest
> operations.
> 
> The mirror VM support is enabled by adding a mirrorvcpus=N
> suboption to -smp, which also designates a few vcpus (normally 1)
> to the mirror VM.
> 
> Example usage for starting a 4-vcpu guest, of which 1 vcpu is marked as
> mirror vcpu.
> 
>     qemu-system-x86_64 -smp 4,mirrorvcpus=1 ...
> 
> Ashish Kalra (7):
>   kvm: Add Mirror VM ioctl and enable cap interfaces.
>   kvm: Add Mirror VM support.
>   kvm: create Mirror VM and share primary VM's encryption context.
>   softmmu/cpu: Skip mirror vcpu's for pause, resume and synchronization.
>   kvm/apic: Disable in-kernel APIC support for mirror vcpu's.
>   hw/acpi: disable modern CPU hotplug interface for mirror vcpu's
>   hw/i386/pc: reduce fw_cfg boot cpu count taking into account mirror
>     vcpu's.
> 
> Dov Murik (5):
>   machine: Add mirrorvcpus=N suboption to -smp
>   hw/boards: Add mirror_vcpu flag to CPUArchId
>   hw/i386: Mark mirror vcpus in possible_cpus
>   cpu: Add boolean mirror_vcpu field to CPUState
>   hw/i386: Set CPUState.mirror_vcpu=true for mirror vcpus
> 
> Tobin Feldman-Fitzthum (1):
>   hw/acpi: Don't include mirror vcpus in ACPI tables
> 
>  accel/kvm/kvm-accel-ops.c |  45 ++++++-
>  accel/kvm/kvm-all.c       | 244 +++++++++++++++++++++++++++++++++++++-
>  accel/kvm/kvm-cpus.h      |   2 +
>  hw/acpi/cpu.c             |  21 +++-
>  hw/core/cpu-common.c      |   1 +
>  hw/core/machine.c         |   7 ++
>  hw/i386/acpi-build.c      |   5 +
>  hw/i386/acpi-common.c     |   5 +
>  hw/i386/kvm/apic.c        |  15 +++
>  hw/i386/pc.c              |  10 ++
>  hw/i386/x86.c             |  11 +-
>  include/hw/acpi/cpu.h     |   1 +
>  include/hw/boards.h       |   3 +
>  include/hw/core/cpu.h     |   3 +
>  include/hw/i386/x86.h     |   3 +-
>  include/sysemu/kvm.h      |  15 +++
>  qapi/machine.json         |   5 +-
>  softmmu/cpus.c            |  27 +++++
>  softmmu/vl.c              |   3 +
>  target/i386/kvm/kvm.c     |  42 +++++++
>  20 files changed, 459 insertions(+), 9 deletions(-)
>