KVM: arm64: Deduplicate ASID retrieval code

We currently have three versions of the ASID retrieval code, one
in the S1 walker, and two in the VNCR handling (although the last
two are limited to the EL2&0 translation regime).

Make this code common, and take this opportunity to also simplify
the code a bit while switching over to the TTBRx_EL1_ASID macro.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260225104718.14209-1-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/include/asm/kvm_nested.h

@@ -397,6 +397,8 @@ int kvm_vcpu_allocate_vncr_tlb(struct kvm_vcpu *vcpu);
 int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu);
 void kvm_handle_s1e2_tlbi(struct kvm_vcpu *vcpu, u32 inst, u64 val);
 
+u16 get_asid_by_regime(struct kvm_vcpu *vcpu, enum trans_regime regime);
+
 #define vncr_fixmap(c)						\
 	({							\
 		u32 __c = (c);					\

arch/arm64/kvm/at.c

@@ -540,31 +540,8 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 	wr->pa |= va & GENMASK_ULL(va_bottom - 1, 0);
 
 	wr->nG = (wi->regime != TR_EL2) && (desc & PTE_NG);
-	if (wr->nG) {
-		u64 asid_ttbr, tcr;
-
-		switch (wi->regime) {
-		case TR_EL10:
-			tcr = vcpu_read_sys_reg(vcpu, TCR_EL1);
-			asid_ttbr = ((tcr & TCR_A1) ?
-				     vcpu_read_sys_reg(vcpu, TTBR1_EL1) :
-				     vcpu_read_sys_reg(vcpu, TTBR0_EL1));
-			break;
-		case TR_EL20:
-			tcr = vcpu_read_sys_reg(vcpu, TCR_EL2);
-			asid_ttbr = ((tcr & TCR_A1) ?
-				     vcpu_read_sys_reg(vcpu, TTBR1_EL2) :
-				     vcpu_read_sys_reg(vcpu, TTBR0_EL2));
-			break;
-		default:
-			BUG();
-		}
-
-		wr->asid = FIELD_GET(TTBR_ASID_MASK, asid_ttbr);
-		if (!kvm_has_feat_enum(vcpu->kvm, ID_AA64MMFR0_EL1, ASIDBITS, 16) ||
-		    !(tcr & TCR_ASID16))
-			wr->asid &= GENMASK(7, 0);
-	}
+	if (wr->nG)
+		wr->asid = get_asid_by_regime(vcpu, wi->regime);
 
 	return 0;
 

arch/arm64/kvm/nested.c

@@ -854,6 +854,33 @@ int kvm_inject_s2_fault(struct kvm_vcpu *vcpu, u64 esr_el2)
 	return kvm_inject_nested_sync(vcpu, esr_el2);
 }
 
+u16 get_asid_by_regime(struct kvm_vcpu *vcpu, enum trans_regime regime)
+{
+	enum vcpu_sysreg ttbr_elx;
+	u64 tcr;
+	u16 asid;
+
+	switch (regime) {
+	case TR_EL10:
+		tcr = vcpu_read_sys_reg(vcpu, TCR_EL1);
+		ttbr_elx = (tcr & TCR_A1) ? TTBR1_EL1 : TTBR0_EL1;
+		break;
+	case TR_EL20:
+		tcr = vcpu_read_sys_reg(vcpu, TCR_EL2);
+		ttbr_elx = (tcr & TCR_A1) ? TTBR1_EL2 : TTBR0_EL2;
+		break;
+	default:
+		BUG();
+	}
+
+	asid = FIELD_GET(TTBRx_EL1_ASID, vcpu_read_sys_reg(vcpu, ttbr_elx));
+	if (!kvm_has_feat_enum(vcpu->kvm, ID_AA64MMFR0_EL1, ASIDBITS, 16) ||
+	    !(tcr & TCR_ASID16))
+		asid &= GENMASK(7, 0);
+
+	return asid;
+}
+
 static void invalidate_vncr(struct vncr_tlb *vt)
 {
 	vt->valid = false;
@@ -1333,20 +1360,8 @@ static bool kvm_vncr_tlb_lookup(struct kvm_vcpu *vcpu)
 	if (read_vncr_el2(vcpu) != vt->gva)
 		return false;
 
-	if (vt->wr.nG) {
-		u64 tcr = vcpu_read_sys_reg(vcpu, TCR_EL2);
-		u64 ttbr = ((tcr & TCR_A1) ?
-			    vcpu_read_sys_reg(vcpu, TTBR1_EL2) :
-			    vcpu_read_sys_reg(vcpu, TTBR0_EL2));
-		u16 asid;
-
-		asid = FIELD_GET(TTBR_ASID_MASK, ttbr);
-		if (!kvm_has_feat_enum(vcpu->kvm, ID_AA64MMFR0_EL1, ASIDBITS, 16) ||
-		    !(tcr & TCR_ASID16))
-			asid &= GENMASK(7, 0);
-
-		return asid == vt->wr.asid;
-	}
+	if (vt->wr.nG)
+		return get_asid_by_regime(vcpu, TR_EL20) == vt->wr.asid;
 
 	return true;
 }
@@ -1449,21 +1464,8 @@ static void kvm_map_l1_vncr(struct kvm_vcpu *vcpu)
 	if (read_vncr_el2(vcpu) != vt->gva)
 		return;
 
-	if (vt->wr.nG) {
-		u64 tcr = vcpu_read_sys_reg(vcpu, TCR_EL2);
-		u64 ttbr = ((tcr & TCR_A1) ?
-			    vcpu_read_sys_reg(vcpu, TTBR1_EL2) :
-			    vcpu_read_sys_reg(vcpu, TTBR0_EL2));
-		u16 asid;
-
-		asid = FIELD_GET(TTBR_ASID_MASK, ttbr);
-		if (!kvm_has_feat_enum(vcpu->kvm, ID_AA64MMFR0_EL1, ASIDBITS, 16) ||
-		    !(tcr & TCR_ASID16))
-			asid &= GENMASK(7, 0);
-
-		if (asid != vt->wr.asid)
-			return;
-	}
+	if (vt->wr.nG && get_asid_by_regime(vcpu, TR_EL20) != vt->wr.asid)
+		return;
 
 	vt->cpu = smp_processor_id();