[RFC PATCH 20/26] kvm: arm64: Add CPU entry point in nVHE hyp

[David Brazdil <dbrazdil@google.com>]

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 <dbrazdil@google.com>
---
 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 9eecb37db6df..8350b95ce94e 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;
 };
 
 enum kvm_nvhe_psci_state {
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 1726cc44b3ee..dd297a1a8f82 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	.
+
+	/* Initialize EL2 CPU state to sane values. */
+	mov	x29, x0
+	init_el2_state nvhe
+	mov	x0, x29
+
+	/*
+	 * Load hyp VA of C entry function. Must do so before switching on the
+	 * MMU because the struct pointer is PA and not identity-mapped in hyp.
+	 */
+	ldr	x29, [x0, #NVHE_INIT_PSCI_CPU_ENTRY_FN]
+
+	/* Enable MMU, set vectors and stack. */
+	bl	___kvm_hyp_init
+
+	/* Leave idmap. */
+	br	x29
+SYM_CODE_END(__kvm_hyp_cpu_entry)
+
 SYM_CODE_START(__kvm_handle_stub_hvc)
 	cmp	x0, #HVC_SOFT_RESTART
 	b.ne	1f
-- 
2.29.1.341.ge80a0c044ae-goog

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