KVM: arm64: Add a generic synchronous exception injection primitive

Maybe in a surprising way, we don't currently have a generic way
to inject a synchronous exception at the EL the vcpu is currently
running at.

Extract such primitive from the UNDEF injection code.

Reviewed-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Yuan Yao <yaoyuan@linux.alibaba.com>
Link: https://patch.msgid.link/20260108173233.2911955-4-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/include/asm/kvm_emulate.h

@@ -45,6 +45,7 @@ bool kvm_condition_valid32(const struct kvm_vcpu *vcpu);
 void kvm_skip_instr32(struct kvm_vcpu *vcpu);
 
 void kvm_inject_undefined(struct kvm_vcpu *vcpu);
+void kvm_inject_sync(struct kvm_vcpu *vcpu, u64 esr);
 int kvm_inject_serror_esr(struct kvm_vcpu *vcpu, u64 esr);
 int kvm_inject_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr);
 void kvm_inject_size_fault(struct kvm_vcpu *vcpu);

arch/arm64/kvm/inject_fault.c

@@ -162,20 +162,24 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
 	vcpu_write_sys_reg(vcpu, esr, exception_esr_elx(vcpu));
 }
 
+void kvm_inject_sync(struct kvm_vcpu *vcpu, u64 esr)
+{
+	pend_sync_exception(vcpu);
+	vcpu_write_sys_reg(vcpu, esr, exception_esr_elx(vcpu));
+}
+
 static void inject_undef64(struct kvm_vcpu *vcpu)
 {
 	u64 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT);
 
-	pend_sync_exception(vcpu);
-
 	/*
 	 * Build an unknown exception, depending on the instruction
 	 * set.
 	 */
 	if (kvm_vcpu_trap_il_is32bit(vcpu))
 		esr |= ESR_ELx_IL;
 
-	vcpu_write_sys_reg(vcpu, esr, exception_esr_elx(vcpu));
+	kvm_inject_sync(vcpu, esr);
 }
 
 #define DFSR_FSC_EXTABT_LPAE	0x10