Re: [PATCH v16 11/45] KVM: arm64: CCA: Check for RMI support at KVM init

Hi Steven,

On Mon, 3 Aug 2026 at 14:45, Steven Price <[email protected]> wrote:
...
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index bae2c4f92ef5..1a5e15040111 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -27,6 +27,7 @@
>  #include <asm/fpsimd.h>
>  #include <asm/kvm.h>
>  #include <asm/kvm_asm.h>
> +#include <asm/kvm_rmi.h>
>  #include <asm/vncr_mapping.h>
>
>  #define __KVM_HAVE_ARCH_INTC_INITIALIZED
> @@ -424,6 +425,9 @@ struct kvm_arch {
>         /* Nested virtualization info */
>         struct dentry *debugfs_nv_dentry;
>  #endif
> +
> +       bool is_realm;
> +       struct realm realm;
>  };

Marc suggested at v10 making the pKVM and CCA state here a union,
given the two are exclusive, and I believe you acked it [1]. Was there
an issue with it, or did it just get lost across the respins?

Cheers,
/fuad

[1] https://lore.kernel.org/all/[email protected]/



>
>  struct kvm_vcpu_fault_info {
> diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
> new file mode 100644
> index 000000000000..57d24b244c95
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_rmi.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2023-2026 ARM Ltd.
> + */
> +
> +#ifndef __ASM_KVM_RMI_H
> +#define __ASM_KVM_RMI_H
> +
> +/**
> + * struct realm - Additional per VM data for a Realm
> + */
> +struct realm {
> +};
> +
> +void kvm_init_rmi(void);
> +
> +#endif /* __ASM_KVM_RMI_H */
> diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
> index b546703c3ab9..92cec42952f4 100644
> --- a/arch/arm64/include/asm/virt.h
> +++ b/arch/arm64/include/asm/virt.h
> @@ -87,6 +87,7 @@ void __hyp_reset_vectors(void);
>  bool is_kvm_arm_initialised(void);
>
>  DECLARE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);
> +DECLARE_STATIC_KEY_FALSE(kvm_rmi_is_available);
>
>  static inline bool is_pkvm_initialized(void)
>  {
> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index 449154f9a485..189e8ad78b22 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -37,6 +37,7 @@ menuconfig KVM
>         select SCHED_INFO
>         select GUEST_PERF_EVENTS if PERF_EVENTS
>         select KVM_GUEST_MEMFD
> +       select ARM_RMM
>         help
>           Support hosting virtualized guest machines.
>
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 59612d2f277c..ed3cf30eb06e 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -16,7 +16,7 @@ CFLAGS_handle_exit.o += -Wno-override-init
>  kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
>          inject_fault.o va_layout.o handle_exit.o config.o \
>          guest.o debug.o reset.o sys_regs.o stacktrace.o \
> -        vgic-sys-reg-v3.o fpsimd.o pkvm.o \
> +        vgic-sys-reg-v3.o fpsimd.o pkvm.o rmi.o \
>          arch_timer.o trng.o vmid.o emulate-nested.o nested.o at.o \
>          vgic/vgic.o vgic/vgic-init.o \
>          vgic/vgic-irqfd.o vgic/vgic-v2.o \
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 50adfff75be8..b961c22fce3d 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -42,6 +42,7 @@
>  #include <asm/kvm_nested.h>
>  #include <asm/kvm_pkvm.h>
>  #include <asm/kvm_ptrauth.h>
> +#include <asm/kvm_rmi.h>
>  #include <asm/sections.h>
>  #include <asm/stacktrace/nvhe.h>
>
> @@ -111,6 +112,8 @@ long kvm_get_cap_for_kvm_ioctl(unsigned int ioctl, long *ext)
>         return -EINVAL;
>  }
>
> +DEFINE_STATIC_KEY_FALSE(kvm_rmi_is_available);
> +
>  DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
>
>  DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_base);
> @@ -3019,6 +3022,8 @@ static __init int kvm_arm_init(void)
>
>         in_hyp_mode = is_kernel_in_hyp_mode();
>
> +       kvm_init_rmi();
> +
>         if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE) ||
>             cpus_have_final_cap(ARM64_WORKAROUND_1508412))
>                 kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
> diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
> new file mode 100644
> index 000000000000..384991d69f78
> --- /dev/null
> +++ b/arch/arm64/kvm/rmi.c
> @@ -0,0 +1,24 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023-2026 ARM Ltd.
> + */
> +
> +#include <linux/kvm_host.h>
> +
> +#include <asm/rmi_cmds.h>
> +#include <asm/virt.h>
> +
> +void kvm_init_rmi(void)
> +{
> +       /*
> +        * TODO: Support Realm guests in nVHE mode, this will require adding
> +        * EL2 stub(s) for REC entry and possibly other things.
> +        */
> +       if (!is_kernel_in_hyp_mode())
> +               return;
> +
> +       if (!is_rmi_available())
> +               return;
> +
> +       /* Future patch will enable static branch kvm_rmi_is_available */
> +}
> --
> 2.43.0
>