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

[Mathieu Poirier <mathieu.poirier@linaro.org>]

Hi Kohei - apologies for the delayed reply.

On Thu, Jul 30, 2026 at 02:11:57PM +0900, Kohei Enju wrote:
> 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
>

git.codelinaro.org is no longer accessible to me.  Please see if you can point
me to the same patch in this repository:

https://gitlab.com/Linaro/cca-public/qemu/-/commits/cca/2025-09-12?ref_type=heads

 
> 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/20260513131757.116630-1-steven.price@arm.com/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.