kvm: arm64: Duplicate arm64_ssbd_callback_required for nVHE hyp

Hyp keeps track of which cores require SSBD callback by accessing a
kernel-proper global variable. Create an nVHE symbol of the same name
and copy the value from kernel proper to nVHE as KVM is being enabled
on a core.

Done in preparation for separating percpu memory owned by kernel
proper and nVHE.
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200922204910.7265-8-dbrazdil@google.com

arch/arm64/include/asm/kvm_mmu.h

@@ -529,6 +529,7 @@ static inline int kvm_map_vectors(void)
 
 #ifdef CONFIG_ARM64_SSBD
 DECLARE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
+DECLARE_KVM_NVHE_PER_CPU(u64, arm64_ssbd_callback_required);
 
 static inline int hyp_map_aux_data(void)
 {
@@ -537,18 +538,29 @@ static inline int hyp_map_aux_data(void)
 	for_each_possible_cpu(cpu) {
 		u64 *ptr;
 
-		ptr = per_cpu_ptr(&arm64_ssbd_callback_required, cpu);
+		ptr = per_cpu_ptr_nvhe_sym(arm64_ssbd_callback_required, cpu);
 		err = create_hyp_mappings(ptr, ptr + 1, PAGE_HYP);
 		if (err)
 			return err;
 	}
 	return 0;
 }
+
+static inline void hyp_init_aux_data(void)
+{
+	u64 *ptr;
+
+	/* Copy arm64_ssbd_callback_required value from kernel to hyp. */
+	ptr = this_cpu_ptr_nvhe_sym(arm64_ssbd_callback_required);
+	*ptr = __this_cpu_read(arm64_ssbd_callback_required);
+}
 #else
 static inline int hyp_map_aux_data(void)
 {
 	return 0;
 }
+
+static inline void hyp_init_aux_data(void) {}
 #endif
 
 #define kvm_phys_to_vttbr(addr)		phys_to_ttbr(addr)

arch/arm64/kernel/image-vars.h

@@ -67,7 +67,6 @@ KVM_NVHE_ALIAS(kvm_patch_vector_branch);
 KVM_NVHE_ALIAS(kvm_update_va_mask);
 
 /* Global kernel state accessed by nVHE hyp code. */
-KVM_NVHE_ALIAS(arm64_ssbd_callback_required);
 KVM_NVHE_ALIAS(kvm_host_data);
 KVM_NVHE_ALIAS(kvm_vgic_global_state);
 

arch/arm64/kvm/arm.c

@@ -1295,6 +1295,9 @@ static void cpu_init_hyp_mode(void)
 	    arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) {
 		kvm_call_hyp_nvhe(__kvm_enable_ssbs);
 	}
+
+	/* Copy information whether SSBD callback is required to hyp. */
+	hyp_init_aux_data();
 }
 
 static void cpu_hyp_reset(void)

arch/arm64/kvm/hyp/nvhe/switch.c

@@ -27,6 +27,9 @@
 #include <asm/processor.h>
 #include <asm/thread_info.h>
 
+/* Non-VHE copy of the kernel symbol. */
+DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
+
 static void __activate_traps(struct kvm_vcpu *vcpu)
 {
 	u64 val;