[PATCH v3 23/24] KVM: arm64: Hide S1PIE registers from userspace when disabled for guests

[Marc Zyngier]

From: Mark Brown <broonie at kernel.org>

When the guest does not support S1PIE we should not allow any access
to the system registers it adds in order to ensure that we do not create
spurious issues with guest migration. Add a visibility operation for these
registers.

Fixes: 86f9de9db178 ("KVM: arm64: Save/restore PIE registers")
Signed-off-by: Mark Brown <broonie at kernel.org>
Link: https://lore.kernel.org/r/20240822-kvm-arm64-hide-pie-regs-v2-3-376624fa829c@kernel.org
Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/include/asm/kvm_host.h |  3 +++
 arch/arm64/kvm/sys_regs.c         | 35 ++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index cc9082e9ecf8b..326d2f601d693 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1492,4 +1492,7 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
 #define kvm_has_tcr2(k)				\
 	(kvm_has_feat((k), ID_AA64MMFR3_EL1, TCRX, IMP))
 
+#define kvm_has_s1pie(k)				\
+	(kvm_has_feat((k), ID_AA64MMFR3_EL1, S1PIE, IMP))
+
 #endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 11fcc796be334..d8fb894832776 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2355,6 +2355,27 @@ static unsigned int tcr2_el2_visibility(const struct kvm_vcpu *vcpu,
 	return tcr2_visibility(vcpu, rd);
 }
 
+static unsigned int s1pie_visibility(const struct kvm_vcpu *vcpu,
+				     const struct sys_reg_desc *rd)
+{
+	if (kvm_has_s1pie(vcpu->kvm))
+		return 0;
+
+	return REG_HIDDEN;
+}
+
+static unsigned int s1pie_el2_visibility(const struct kvm_vcpu *vcpu,
+					 const struct sys_reg_desc *rd)
+{
+	unsigned int r;
+
+	r = el2_visibility(vcpu, rd);
+	if (r)
+		return r;
+
+	return s1pie_visibility(vcpu, rd);
+}
+
 /*
  * Architected system registers.
  * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
@@ -2592,8 +2613,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_PMMIR_EL1), trap_raz_wi },
 
 	{ SYS_DESC(SYS_MAIR_EL1), access_vm_reg, reset_unknown, MAIR_EL1 },
-	{ SYS_DESC(SYS_PIRE0_EL1), NULL, reset_unknown, PIRE0_EL1 },
-	{ SYS_DESC(SYS_PIR_EL1), NULL, reset_unknown, PIR_EL1 },
+	{ SYS_DESC(SYS_PIRE0_EL1), NULL, reset_unknown, PIRE0_EL1,
+	  .visibility = s1pie_visibility },
+	{ SYS_DESC(SYS_PIR_EL1), NULL, reset_unknown, PIR_EL1,
+	  .visibility = s1pie_visibility },
 	{ SYS_DESC(SYS_AMAIR_EL1), access_vm_reg, reset_amair_el1, AMAIR_EL1 },
 
 	{ SYS_DESC(SYS_LORSA_EL1), trap_loregion },
@@ -2890,8 +2913,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	EL2_REG(HPFAR_EL2, access_rw, reset_val, 0),
 
 	EL2_REG(MAIR_EL2, access_rw, reset_val, 0),
-	EL2_REG(PIRE0_EL2, check_s1pie_access_rw, reset_val, 0),
-	EL2_REG(PIR_EL2, check_s1pie_access_rw, reset_val, 0),
+	EL2_REG_FILTERED(PIRE0_EL2, check_s1pie_access_rw, reset_val, 0,
+			 s1pie_el2_visibility),
+	EL2_REG_FILTERED(PIR_EL2, check_s1pie_access_rw, reset_val, 0,
+			 s1pie_el2_visibility),
 	EL2_REG(AMAIR_EL2, access_rw, reset_val, 0),
 
 	EL2_REG(VBAR_EL2, access_rw, reset_val, 0),
@@ -4766,7 +4791,7 @@ void kvm_calculate_traps(struct kvm_vcpu *vcpu)
 		kvm->arch.fgu[HFGITR_GROUP] |= (HFGITR_EL2_ATS1E1RP |
 						HFGITR_EL2_ATS1E1WP);
 
-	if (!kvm_has_feat(kvm, ID_AA64MMFR3_EL1, S1PIE, IMP))
+	if (!kvm_has_s1pie(kvm))
 		kvm->arch.fgu[HFGxTR_GROUP] |= (HFGxTR_EL2_nPIRE0_EL1 |
 						HFGxTR_EL2_nPIR_EL1);
 
-- 
2.39.2