Re: [RFC v4 01/24] linux-headers: Add RME related definitions

[Gavin Shan <gshan@redhat.com>]

Hi Mathieu,

On 9/4/26 5:35 AM, Mathieu Poirier wrote:
> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> 
> This is a temporary patch intended for testing purposes only. It provides
> definitions related to supporting Realms by the QEMU-VMM.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>   linux-headers/asm-arm64/kvm.h |  9 +++++++++
>   linux-headers/linux/kvm.h     | 10 +++++++++-
>   2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/linux-headers/asm-arm64/kvm.h b/linux-headers/asm-arm64/kvm.h
> index 6aefe7973814..4c08631ec7d2 100644
> --- a/linux-headers/asm-arm64/kvm.h
> +++ b/linux-headers/asm-arm64/kvm.h
> @@ -208,6 +208,15 @@ struct kvm_arm_counter_offset {
>   	__u64 reserved;
>   };
>   
> +#define KVM_ARM_RMI_POPULATE_FLAGS_MEASURE     (1 << 0)
> +struct kvm_arm_rmi_populate {
> +	__u64 base;
> +	__u64 size;
> +	__u64 source_uaddr;
> +	__u32 flags;
> +	__u32 reserved;
> +};
> +
>   #define KVM_ARM_TAGS_TO_GUEST		0
>   #define KVM_ARM_TAGS_FROM_GUEST		1
>   
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index 29f81c05aca2..8b7627f11447 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -689,14 +689,19 @@ struct kvm_enable_cap {
>    * address size for the VM. Bits[7-0] are reserved for the guest
>    * PA size shift (i.e, log2(PA_Size)). For backward compatibility,
>    * value 0 implies the default IPA size, 40bits.
> + *
> + * Bits[30-31] are reserved for the VM type
>    */
>   #define KVM_VM_TYPE_ARM_IPA_SIZE_MASK	0xffULL
>   #define KVM_VM_TYPE_ARM_IPA_SIZE(x)		\
>   	((x) & KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
>   
> +#define KVM_VM_TYPE_ARM_NORMAL		0
> +#define KVM_VM_TYPE_ARM_REALM		(1UL << 30)
>   #define KVM_VM_TYPE_ARM_PROTECTED	(1UL << 31)
>   #define KVM_VM_TYPE_ARM_MASK		(KVM_VM_TYPE_ARM_IPA_SIZE_MASK | \
> -					 KVM_VM_TYPE_ARM_PROTECTED)
> +					 KVM_VM_TYPE_ARM_PROTECTED | \
> +					 KVM_VM_TYPE_ARM_REALM)
>   
>   /*
>    * ioctls for /dev/kvm fds:
> @@ -719,6 +724,8 @@ struct kvm_enable_cap {
>   #define KVM_GET_EMULATED_CPUID	  _IOWR(KVMIO, 0x09, struct kvm_cpuid2)
>   #define KVM_GET_MSR_FEATURE_INDEX_LIST    _IOWR(KVMIO, 0x0a, struct kvm_msr_list)
>   
> +#define KVM_ARM_RMI_POPULATE	  _IOWR(KVMIO, 0xd7, struct kvm_arm_rmi_populate)
> +
>   /*
>    * Extension capability list.
>    */
> @@ -988,6 +995,7 @@ struct kvm_enable_cap {
>   #define KVM_CAP_S390_HPAGE_2G 249
>   #define KVM_CAP_PPC_COMPAT_CAPS 250
>   #define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 251
> +#define KVM_CAP_ARM_RMI 252
>   

Both KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES and KVM_CAP_ARM_RMI aren't consistent to
the definitions in Steven Price's (v16) host series [1]. They need corrections as
below. Otherwise, realm VM can't be started and the following errors are raised by
qemu.

[1] https://lore.kernel.org/kvm/20260803134403.80630-14-steven.price@arm.com/

root@host:~# qemu-system-aarch64 -enable-kvm                  \
-object rme-guest,id=rme0,convert-in-place=on                 \
-machine virt,gic-version=3,confidential-guest-support=rme0   \
-m 2G -cpu host                                               \
-smp maxcpus=4,cpus=4,sockets=1,clusters=1,cores=2,threads=2  \
-object memory-backend-guest-memfd,id=mem0,size=2G,share=on   \
-numa node,nodeid=0,cpus=0-3,memdev=mem0                      \
-serial mon:stdio -monitor none -nographic -nodefaults        \
-kernel /mnt/linux/arch/arm64/boot/Image                      \
-initrd /mnt/buildroot/output/images/rootfs.cpio.xz           \
-append earlycon=pl011,mmio,0x10009000000
     :
qemu-system-aarch64: VM doesn't support Realms
qemu-system-aarch64: failed to initialize kvm: No such device


-#define KVM_CAP_PPC_COMPAT_CAPS 250
-#define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 251
-#define KVM_CAP_ARM_RMI 252
+#define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 250
+#define KVM_CAP_ARM_RMI 251

>   struct kvm_irq_routing_irqchip {
>   	__u32 irqchip;

Thanks,
Gavin