[PATCH v4 21/29] KVM: arm64: Add NVHCR_EL2 handling to the sysreg array

Expose NVHCR_EL2 to userspace, and treat the direct access as UNDEF,
as that would only outline a bug in our exception routing.

The generic accessors are also updated to deal with the relatively
uncommon location of that register.

Signed-off-by: Marc Zyngier <[email protected]>
---
 arch/arm64/kvm/sys_regs.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 9439c5b2b1fe8..0aeb2e736fde3 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -221,6 +221,20 @@ static void locate_register(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg,
 		if (is_hyp_ctxt(vcpu) && vcpu_el2_e2h_is_set(vcpu))
 			loc->loc = SR_LOC_SPECIAL;
 		break;
+	case NVHCR_EL2:
+		/*
+		 * Yes, NVHCR_EL2 maps to itself when loaded in nested
+		 * context. If you feel like the architecture is double
+		 * backing on itself upside down, you're not alone.
+		 */
+		WARN_ON_ONCE(!kvm_has_nv3(vcpu->kvm));
+		if (is_hyp_ctxt(vcpu)) {
+			loc->loc = SR_LOC_MEMORY;
+		} else {
+			loc->loc = SR_LOC_LOADED | SR_LOC_MAPPED;
+			loc->map_reg = NVHCR_EL2;
+		}
+		break;
 	default:
 		loc->loc = locate_direct_register(vcpu, reg);
 	}
@@ -260,6 +274,7 @@ static u64 read_sr_from_cpu(enum vcpu_sysreg reg)
 	case DACR32_EL2:	val = read_sysreg_s(SYS_DACR32_EL2);	break;
 	case IFSR32_EL2:	val = read_sysreg_s(SYS_IFSR32_EL2);	break;
 	case DBGVCR32_EL2:	val = read_sysreg_s(SYS_DBGVCR32_EL2);	break;
+	case NVHCR_EL2:		val = read_sysreg_s(SYS_NVHCR_EL2);	break;
 	default:		WARN_ON_ONCE(1);
 	}
 
@@ -298,6 +313,7 @@ static void write_sr_to_cpu(enum vcpu_sysreg reg, u64 val)
 	case DACR32_EL2:	write_sysreg_s(val, SYS_DACR32_EL2);	break;
 	case IFSR32_EL2:	write_sysreg_s(val, SYS_IFSR32_EL2);	break;
 	case DBGVCR32_EL2:	write_sysreg_s(val, SYS_DBGVCR32_EL2);	break;
+	case NVHCR_EL2:		write_sysreg_s(val, SYS_NVHCR_EL2);	break;
 	default:		WARN_ON_ONCE(1);
 	}
 }
@@ -2861,6 +2877,16 @@ static unsigned int vncr_el2_visibility(const struct kvm_vcpu *vcpu,
 	return REG_HIDDEN;
 }
 
+static unsigned int nvhcr_el2_visibility(const struct kvm_vcpu *vcpu,
+					const struct sys_reg_desc *rd)
+{
+	if (el2_visibility(vcpu, rd) == 0 &&
+	    kvm_has_feat(vcpu->kvm, ID_AA64MMFR4_EL1, NV_frac, NV3))
+		return 0;
+
+	return REG_HIDDEN;
+}
+
 static unsigned int sctlr2_visibility(const struct kvm_vcpu *vcpu,
 				      const struct sys_reg_desc *rd)
 {
@@ -3774,6 +3800,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 			 sve_el2_visibility),
 
 	EL2_REG_VNCR(HCRX_EL2, reset_val, 0),
+	EL2_REG_FILTERED(NVHCR_EL2, undef_access, reset_val, 0,
+			 nvhcr_el2_visibility),
 
 	EL2_REG(TTBR0_EL2, access_rw, reset_val, 0),
 	EL2_REG(TTBR1_EL2, access_rw, reset_val, 0),
-- 
2.47.3