Re: [RFC v2 00/24] Add Realm support to QEMU-VMM

On 07/28 13:26, Mathieu Poirier wrote:
> This patchset provides minimal functionality to start a Realm VM
> from an Arm RME capable host using the following command line:
> 
> qemu-system-aarch64 \
>  -M confidential-guest-support=rme0 -object rme-guest,id=rme0 \
>  -cpu host -M virt -enable-kvm -M gic-version=3,its=on -nodefaults ..
> 
> It is a refactoring of Jean-Philippe Brucker's initial work dating from a while
> back.  It is compatible with Steven Price's v14 revision [1] of his work adding
> CCA support to KVM.
> 
> * We are currently working on rebasing the work to v15.
> 
> It was tested on the QEMU SBSA machine.  For convenience, a repository is hosted
> here [2], along with the TF-A [3], RMM [4] and Linux kernel [5] for the SBSA
> machine (compatible with Steven's v14 patchset).
> 
> Instructions to compile and run the entire stack can be found here [6].
> 
> Device Assignment is not included.
> 
> Thanks,
> Mathieu

Hi Mathieu, thank you for your work on upstreaming CCA support. I've
tested this series in QEMU-TCG(x-rme=on) environments and confirmed
that the basic functionality works well.

I have a question about a QMP command for querying CCA capabilities.

Jean's tree contains the following commit adding such a QMP command. Was
this functionality intentionally omitted from this series?
https://git.codelinaro.org/linaro/dcap/qemu/-/commit/41f7852cc8590a38c47299a35a7238da09ff9a12

We are interested in adding this functionality because we are also
planning to upstream CCA support for libvirt, which will need a QMP
interface to query the CCA capabilities exposed by QEMU.

Since the Linux kernel dropped some configuration parameters such as the
hash algorithm, I need to rework the implementation of that QMP command
a bit. If it's okay with you, I'd be happy to send out the reworked
patch based on this series.

Thanks,
Kohei

> 
> [1]. https://lore.kernel.org/kvm/[email protected]/T/#m06dd14216aaf76acab65b0a76fb84653141ea64f
> [2]. https://gitlab.com/Linaro/cca-public/qemu/-/tree/upstream-v2?ref_type=heads
> [3]. https://gitlab.com/Linaro/cca-public/tf-a/trusted-firmware-a/-/tree/cca/v13?ref_type=heads
> [4]. https://gitlab.com/Linaro/cca-public/rmm/-/tree/cca/v14?ref_type=heads
> [5]. https://gitlab.com/Linaro/cca-public/linux/-/tree/upstream-v2?ref_type=heads 
> [6]. https://gitlab.com/Linaro/cca-public/build-instructions
> 
> RFC v1:
> https://lists.gnu.org/archive/html/qemu-devel/2026-07/msg02307.html
> 
> Changes for V2:
> - Fixed linux headers to include correct bit shift for Realm VM (Gavin).
> - Removed obsolete rme-guest options (Markus).
> - Set ConfidentialGuestSupportClass::kvm_init() to kvm_arm_rme_init() (Gavin).
> - Got rid of kvm_arm_rme_vm_type() (Gavin).
> - Used kvm_vm_check_extension() instead of kvm_check_extension() to avoid
>   error message when starting a Realm (Gavin).
> - Removed obsolete kvm_arm_rme_init_guest_ram() (Gavin).
> - Collected A-B and R-B.