KVM: arm64: pkvm: Use direct function pointers for cpu_{on,resume}

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.

Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260321212419.2803972-5-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

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 a1ad12c72ebf..f4c769857fdf 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 2e80fcbff2df..64296b31da73 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 c3e196fb8b18..5aeb5b453a59 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(&suspend_args);
+
+	__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))