Re: [PATCH v22 05/23] KVM: arm64: Track the type of VM in kvm_arch

[Gavin Shan <gshan@redhat.com>]

On 10/5/26 7:07 PM, Suzuki K Poulose wrote:
> KVM arm64 has different types of VMs with all the different modes in which
> the hypervisor code can be run. e.g., VHE, nVHE, pKVM etc. Then there is
> protected VM and normal VMs with pKVM. We might soon add other types,
> e.g., Arm CCA Realm. So in an effort to make the handling of these
> different types of VMs a bit more friendly to the eyes, add a VM flavor to
> the kvm_arch and we could then add handlers for different operations based
> on the VM type.
> 
> Keep the flavor initialisation at the beginning to allow for the detection
> early enough and fail out on any unsupported requests.
> 
> With that, add wrappers for checking the "type" of a VM and replace the
> existing users with the new wrappers.
> 
> Given we already have the construct of "kvm_vm_is_protected" in the core
> KVM code, use that for all confidential compute guests including Realms
> that we are about to add. Adds __VM_PROTECTED marker vm flavor to draw the
> boundary for "protected VMs". In later patches, we would add Realm VMs,
>   which would also be classified as protected.
> 
> Add a explicit helper to detect if a given VM is a "protected" VM under pKVM.
> Change the existing users that precisely want to check the VM type. These
> include :
>    - kvm_arch_prepare_memory_region - For preventing memslot changes after
>      pVM creation.
> 
> All the others are retained as a wider check for confidential guest VMs.
> These are:
>   - kvm_vm_ioctl_set_counter_offset - For disallowing timer offset
>     configuration
>   - io_mem_abort for dabt handling without valid syndrome information
> 
> Both of which are true for Realms too.
> 
> Realms support is restricted to VHE host and thus "kvm_vm_is_protected()"
> checks in the pkvm hyp specific code doesn't need to change, as the only
> protected guests it deals with is "protected pKVM" guests. To tighten this
> init_pkvm_hyp_vm() restricts the hyp copy of the vm_flavor to the ones it
> supports.
> 
> vcpu_is_protected() usage from nVHE hyp code is tricky, as we need to
> convert the vcpu->kvm to the HYP VA before checking the flavor. This
> involves kern_hyp_va() usage in asm/kvm_host.h. To avoid build breaks,
> include asm/kvm_mmu.h to arm64/kvm/mmio.c.
> 
> While at it move the psci_version around to keep the structure packed.
> 
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Tested-by: Gavin Shan <gshan@redhat.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> Changes since v21:
>   - Drop kern_hyp_va() and restrict nvhe code to always use vcpu_is_protected_pkvm()
>   - Drop kvm_vm_is_unprotected_pkvm() and open code the check
>   - Move psci_version field in kvm_arch around to keep the structure packed
> ---
>   arch/arm64/include/asm/kvm_host.h      | 42 +++++++++++++++++++++++---
>   arch/arm64/include/asm/kvm_pkvm.h      |  4 +--
>   arch/arm64/kvm/arm.c                   | 33 ++++++++++++++++----
>   arch/arm64/kvm/hyp/include/nvhe/pkvm.h |  2 +-
>   arch/arm64/kvm/hyp/nvhe/pkvm.c         |  6 +++-
>   arch/arm64/kvm/hyp/nvhe/switch.c       |  4 +--
>   arch/arm64/kvm/hyp/nvhe/timer-sr.c     |  2 +-
>   arch/arm64/kvm/mmio.c                  |  1 +
>   arch/arm64/kvm/mmu.c                   |  2 +-
>   arch/arm64/kvm/pkvm.c                  |  6 ++--
>   10 files changed, 79 insertions(+), 23 deletions(-)
> 

Reviewed-by: Gavin Shan <gshan@redhat.com>