KVM: PPC: Book3S HV nestedv2: Avoid reloading the tb offset

The kvmppc_get_tb_offset() getter reloads KVMPPC_GSID_TB_OFFSET from the
L0 for nestedv2 host. This is unnecessary as the value does not change.
KVMPPC_GSID_TB_OFFSET also need not be reloaded in
kvmppc_{s,g}et_dec_expires().

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231201132618.555031-3-vaibhav@linux.ibm.com

Author: iamjpn

arch/powerpc/include/asm/kvm_book3s.h

@@ -594,21 +594,24 @@ static inline u##size kvmppc_get_##reg(struct kvm_vcpu *vcpu)		\
 
 
 KVMPPC_BOOK3S_VCORE_ACCESSOR(vtb, 64, KVMPPC_GSID_VTB)
-KVMPPC_BOOK3S_VCORE_ACCESSOR(tb_offset, 64, KVMPPC_GSID_TB_OFFSET)
 KVMPPC_BOOK3S_VCORE_ACCESSOR_GET(arch_compat, 32, KVMPPC_GSID_LOGICAL_PVR)
 KVMPPC_BOOK3S_VCORE_ACCESSOR_GET(lpcr, 64, KVMPPC_GSID_LPCR)
+KVMPPC_BOOK3S_VCORE_ACCESSOR_SET(tb_offset, 64, KVMPPC_GSID_TB_OFFSET)
+
+static inline u64 kvmppc_get_tb_offset(struct kvm_vcpu *vcpu)
+{
+	return vcpu->arch.vcore->tb_offset;
+}
 
 static inline u64 kvmppc_get_dec_expires(struct kvm_vcpu *vcpu)
 {
-	WARN_ON(kvmhv_nestedv2_cached_reload(vcpu, KVMPPC_GSID_TB_OFFSET) < 0);
 	WARN_ON(kvmhv_nestedv2_cached_reload(vcpu, KVMPPC_GSID_DEC_EXPIRY_TB) < 0);
 	return vcpu->arch.dec_expires;
 }
 
 static inline void kvmppc_set_dec_expires(struct kvm_vcpu *vcpu, u64 val)
 {
 	vcpu->arch.dec_expires = val;
-	WARN_ON(kvmhv_nestedv2_cached_reload(vcpu, KVMPPC_GSID_TB_OFFSET) < 0);
 	kvmhv_nestedv2_mark_dirty(vcpu, KVMPPC_GSID_DEC_EXPIRY_TB);
 }