When nVHE hyp starts interception host's PSCI CPU_ON SMCs, it will need
to install KVM on the newly booted CPU before returning to the host. 
Add
an entry point which expects the same kvm_nvhe_init_params struct as 
the
__kvm_hyp_init HVC in the CPU_ON context argument (x0).

The entry point initializes EL2 state with the same init_el2_state 
macro
used by the kernel's entry point. It then initializes KVM using the 
same
helper function used in the __kvm_hyp_init HVC.

When done, the entry point branches to a function provided in the init
params.

Signed-off-by: David Brazdil <redacted>
---
 arch/arm64/include/asm/kvm_asm.h   |  1 +
 arch/arm64/kernel/asm-offsets.c    |  1 +
 arch/arm64/kvm/hyp/nvhe/hyp-init.S | 30 ++++++++++++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_asm.h 

b/arch/arm64/include/asm/kvm_asm.h
index 893327d1e449..efb4872bb29f 100644

--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h

@@ -155,6 +155,7 @@ struct kvm_nvhe_init_params {
 	unsigned long tpidr_el2;
 	unsigned long hyp_stack_ptr;
 	unsigned long vector_ptr;
+	unsigned long psci_cpu_entry_fn;
 };

 /* Translate a kernel address @ptr into its equivalent linear mapping 

*/

diff --git a/arch/arm64/kernel/asm-offsets.c 

b/arch/arm64/kernel/asm-offsets.c
index 0cbb86135c7c..ffc84e68ad97 100644

--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c

@@ -114,6 +114,7 @@ int main(void)
   DEFINE(NVHE_INIT_TPIDR_EL2,	offsetof(struct kvm_nvhe_init_params,

tpidr_el2));
   DEFINE(NVHE_INIT_STACK_PTR,	offsetof(struct kvm_nvhe_init_params,
hyp_stack_ptr));
   DEFINE(NVHE_INIT_VECTOR_PTR,	offsetof(struct kvm_nvhe_init_params,
vector_ptr));
+  DEFINE(NVHE_INIT_PSCI_CPU_ENTRY_FN,	offsetof(struct
kvm_nvhe_init_params, psci_cpu_entry_fn));
 #endif
 #ifdef CONFIG_CPU_PM
   DEFINE(CPU_CTX_SP,		offsetof(struct cpu_suspend_ctx, sp));

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S

b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index 1697d25756e9..f999a35b2c8c 100644

--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S

@@ -6,6 +6,7 @@

 #include <linux/arm-smccc.h>
 #include <linux/linkage.h>
+#include <linux/irqchip/arm-gic-v3.h>

 #include <asm/alternative.h>
 #include <asm/assembler.h>

@@ -159,6 +160,35 @@ alternative_else_nop_endif
 	ret
 SYM_CODE_END(___kvm_hyp_init)

+SYM_CODE_START(__kvm_hyp_cpu_entry)
+	msr	SPsel, #1			// We want to use SP_EL{1,2}
+
+	/*
+	 * Check that the core was booted in EL2. Loop indefinitely if not
+	 * because it cannot be safely given to the host without installing 

KVM.
+	 */
+	mrs	x1, CurrentEL
+	cmp	x1, #CurrentEL_EL2
+	b.ne	.