KVM: arm64: Save chosen hyp vector to a percpu variable

Introduce a percpu variable to hold the address of the selected hyp
vector that will be used with guests. This avoids the selection process
each time a guest is being entered and can be used by nVHE when a
separate vector is introduced for the host.
Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200915104643.2543892-6-ascull@google.com

arch/arm64/include/asm/kvm_hyp.h

@@ -12,6 +12,8 @@
 #include <asm/alternative.h>
 #include <asm/sysreg.h>
 
+DECLARE_PER_CPU(unsigned long, kvm_hyp_vector);
+
 #define read_sysreg_elx(r,nvh,vh)					\
 	({								\
 		u64 reg;						\

arch/arm64/kvm/arm.c

@@ -47,6 +47,7 @@ __asm__(".arch_extension	virt");
 #endif
 
 DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
+DEFINE_PER_CPU(unsigned long, kvm_hyp_vector);
 static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
 
 /* The VMID used in the VTTBR */
@@ -1276,7 +1277,7 @@ static void cpu_init_hyp_mode(void)
 
 	pgd_ptr = kvm_mmu_get_httbr();
 	hyp_stack_ptr = __this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE;
-	vector_ptr = (unsigned long)kvm_get_hyp_vector();
+	vector_ptr = __this_cpu_read(kvm_hyp_vector);
 
 	/*
 	 * Call initialization code, and switch to the full blown HYP code.
@@ -1309,6 +1310,8 @@ static void cpu_hyp_reinit(void)
 
 	cpu_hyp_reset();
 
+	__this_cpu_write(kvm_hyp_vector, (unsigned long)kvm_get_hyp_vector());
+
 	if (is_kernel_in_hyp_mode())
 		kvm_timer_init_vhe();
 	else

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

@@ -59,7 +59,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 
 	write_sysreg(val, cpacr_el1);
 
-	write_sysreg(kvm_get_hyp_vector(), vbar_el1);
+	write_sysreg(__this_cpu_read(kvm_hyp_vector), vbar_el1);
 }
 NOKPROBE_SYMBOL(__activate_traps);