On Mon, Dec 04, 2023 at 03:38:30AM +0000, Duan, Zhenzhong wrote:
-----Original Message----- From: Jonathon Jongsma <jjongsma@redhat.com> Sent: Saturday, December 2, 2023 6:30 AM Subject: Re: [PATCH rfcv3 00/11] LIBVIRT: X86: TDX support
Hello,
Thanks for the submission. A few initial general comments:
Hi,
This series brings libvirt the x86 TDX support.
* What's TDX? TDX stands for Trust Domain Extensions which isolates VMs from the virtual-machine manager (VMM)/hypervisor and any other software on the platform.
To support TDX, multiple software components, not only KVM but also QEMU, guest Linux and virtual bios, need to be updated. For more details, please check link[1], there are TDX spec links and public repository link at github for each software component.
This patchset is another software component to extend libvirt to support TDX, with which one can start a VM from high level rather than running qemu
On 11/27/23 2:55 AM, Zhenzhong Duan wrote: directly.
* Misc As QEMU use a software emulated way to reset guest which isn't
supported by TDX
guest for security reason. We add a new way to emulate the reset for TDX guest, called "hard reboot". We achieve this by killing old qemu and start a new one.
Can you expand on this a little bit more? What problems do you encounter when you reboot the normal way? I did not notice any patches related to a hard reboot in the v2 patchset that was submitted a while ago.
If we use existing "fake reboot" in libvirt, qmp command "system_reset" isn't supported for TDX guest, because TDX doesn't support resetting each register of vcpu for security except in TDX debug mode. TDX guest will be shutdown instead.
I suspect the same probably applies to SEV.
What other approaches did you consider to solve this issue? The changes to virsh adding a reconnect timeout option for the console command in particular feel hacky to me.
One possible way I can think of is to let qemu do the kill/create job, i.e. destroy TDX vcpus, create new one. This way we can utilize existing "fake reboot" interface between qemu and libvirt.
Yes, I do wonder if there's some reasonable way for QEMU to re-create the KVM VM from scratch, to make this hardware limitation more transparent for all mgmt apps. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|