[PATCH 4/5] KVM: arm64: pkvm: Use direct function pointers for cpu_{on,resume}

[Fuad Tabba]

Hi Marc,

On Sat, 21 Mar 2026 at 21:24, Marc Zyngier <maz at kernel.org> wrote:
>
> Instead of using a boolean to decide whether a CPU is booting or
> resuming, just pass an actual function pointer around.
>
> This makes the code a bit more straightforward to understand.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/include/asm/kvm_asm.h     |  3 ++-
>  arch/arm64/kvm/hyp/nvhe/hyp-init.S   |  9 +++----
>  arch/arm64/kvm/hyp/nvhe/psci-relay.c | 39 +++++++++++++++++-----------
>  3 files changed, 29 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index a1ad12c72ebf1..f4c769857fdfc 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -291,7 +291,8 @@ asmlinkage void __noreturn hyp_panic_bad_stack(void);
>  asmlinkage void kvm_unexpected_el2_exception(void);
>  struct kvm_cpu_context;
>  void handle_trap(struct kvm_cpu_context *host_ctxt);
> -asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on);
> +asmlinkage void __noreturn __kvm_host_psci_cpu_on_entry(void);
> +asmlinkage void __noreturn __kvm_host_psci_cpu_resume_entry(void);
>  void __noreturn __pkvm_init_finalise(void);
>  void kvm_nvhe_prepare_backtrace(unsigned long fp, unsigned long pc);
>  void kvm_patch_vector_branch(struct alt_instr *alt,
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> index 2e80fcbff2dff..64296b31da73d 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> @@ -173,7 +173,7 @@ SYM_CODE_END(___kvm_hyp_init)
>   * x0: struct kvm_nvhe_init_params PA
>   */
>  SYM_CODE_START(kvm_hyp_cpu_entry)
> -       mov     x1, #1                          // is_cpu_on = true
> +       ldr     x29, =__kvm_host_psci_cpu_on_entry
>         b       __kvm_hyp_init_cpu
>
>  /*
> @@ -182,11 +182,10 @@ SYM_CODE_START(kvm_hyp_cpu_entry)
>   * x0: struct kvm_nvhe_init_params PA
>   */
>  SYM_CODE_START(kvm_hyp_cpu_resume)
> -       mov     x1, #0                          // is_cpu_on = false
> +       ldr     x29, =__kvm_host_psci_cpu_resume_entry
>
>  SYM_INNER_LABEL(__kvm_hyp_init_cpu, SYM_L_LOCAL)
>         mov     x28, x0                         // Stash arguments
> -       mov     x29, x1
>
>         /* Check that the core was booted in EL2. */
>         mrs     x0, CurrentEL
> @@ -204,9 +203,7 @@ SYM_INNER_LABEL(__kvm_hyp_init_cpu, SYM_L_LOCAL)
>         bl      ___kvm_hyp_init                 // Clobbers x0..x2
>
>         /* Leave idmap -- using BLR is OK, LR is restored from host context */
> -       mov     x0, x29
> -       ldr     x1, =__kvm_host_psci_cpu_entry
> -       blr     x1
> +       blr     x29
>
>         // The core booted in EL1, or the C code unexpectedly returned.
>         // Either way, KVM cannot be initialized on it.
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index c3e196fb8b18f..cc698ceee9c8c 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -200,23 +200,12 @@ static int psci_system_suspend(u64 func_id, struct kvm_cpu_context *host_ctxt)
>                          __hyp_pa(init_params), 0);
>  }
>
> -asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
> +static void __noreturn __kvm_host_psci_cpu_entry(unsigned long pc, unsigned long r0)
>  {
> -       struct psci_boot_args *boot_args;
> -       struct kvm_cpu_context *host_ctxt;
> -
> -       host_ctxt = host_data_ptr(host_ctxt);
> -
> -       if (is_cpu_on)
> -               boot_args = this_cpu_ptr(&cpu_on_args);
> -       else
> -               boot_args = this_cpu_ptr(&suspend_args);
> -
> -       cpu_reg(host_ctxt, 0) = boot_args->r0;
> -       write_sysreg_el2(boot_args->pc, SYS_ELR);
> +       struct kvm_cpu_context *host_ctxt = host_data_ptr(host_ctxt);
>
> -       if (is_cpu_on)
> -               release_boot_args(boot_args);
> +       cpu_reg(host_ctxt, 0) = r0;
> +       write_sysreg_el2(pc, SYS_ELR);
>
>         write_sysreg_el1(INIT_SCTLR_EL1_MMU_OFF, SYS_SCTLR);
>         write_sysreg(INIT_PSTATE_EL1, SPSR_EL2);
> @@ -224,6 +213,26 @@ asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
>         __host_enter(host_ctxt);
>  }
>
> +asmlinkage void __noreturn __kvm_host_psci_cpu_on_entry(void)
> +{
> +       struct psci_boot_args *boot_args = this_cpu_ptr(&cpu_on_args);
> +       unsigned long pc, r0;
> +
> +       pc = READ_ONCE(boot_args->pc);
> +       r0 = READ_ONCE(boot_args->r0);
> +
> +       release_boot_args(boot_args);
> +
> +       __kvm_host_psci_cpu_entry(pc, r0);
> +}
> +
> +asmlinkage void __noreturn __kvm_host_psci_cpu_resume_entry(void)
> +{
> +       struct psci_boot_args *boot_args = this_cpu_ptr(&cpu_on_args);

This should be suspend_args:
+     struct psci_boot_args *boot_args = this_cpu_ptr(&suspend_args);

With this fixed:

Reviewed-by: Fuad Tabba <tabba at google.com>

Cheers,
/fuad




> +
> +       __kvm_host_psci_cpu_entry(boot_args->pc, boot_args->r0);
> +}
> +
>  static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
>  {
>         if (is_psci_0_1(cpu_off, func_id) || is_psci_0_1(migrate, func_id))
> --
> 2.47.3
>