[PATCH v3 4/7] arm64/kvm: enable pointer authentication cpufeature conditionally

[Amit Daniel Kachhap]

According to userspace settings, pointer authentication cpufeature
is enabled/disabled from guests.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
---
 arch/arm64/kvm/sys_regs.c | 33 +++++++++++++++++++++------------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 6af6c7d..ce6144a 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1055,7 +1055,7 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
 }
 
 /* Read a sanitised cpufeature ID register by sys_reg_desc */
-static u64 read_id_reg(struct sys_reg_desc const *r, bool raz)
+static u64 read_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_desc const *r, bool raz)
 {
 	u32 id = sys_reg((u32)r->Op0, (u32)r->Op1,
 			 (u32)r->CRn, (u32)r->CRm, (u32)r->Op2);
@@ -1066,6 +1066,15 @@ static u64 read_id_reg(struct sys_reg_desc const *r, bool raz)
 			kvm_debug("SVE unsupported for guests, suppressing\n");
 
 		val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
+	} else if (id == SYS_ID_AA64ISAR1_EL1) {
+		const u64 ptrauth_mask = (0xfUL << ID_AA64ISAR1_APA_SHIFT) |
+					 (0xfUL << ID_AA64ISAR1_API_SHIFT) |
+					 (0xfUL << ID_AA64ISAR1_GPA_SHIFT) |
+					 (0xfUL << ID_AA64ISAR1_GPI_SHIFT);
+		if (!kvm_arm_vcpu_ptrauth_allowed(vcpu)) {
+			kvm_debug("ptrauth unsupported for guests, suppressing\n");
+			val &= ~ptrauth_mask;
+		}
 	} else if (id == SYS_ID_AA64MMFR1_EL1) {
 		if (val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))
 			kvm_debug("LORegions unsupported for guests, suppressing\n");
@@ -1086,7 +1095,7 @@ static bool __access_id_reg(struct kvm_vcpu *vcpu,
 	if (p->is_write)
 		return write_to_read_only(vcpu, p, r);
 
-	p->regval = read_id_reg(r, raz);
+	p->regval = read_id_reg(vcpu, r, raz);
 	return true;
 }
 
@@ -1115,17 +1124,17 @@ static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
  * are stored, and for set_id_reg() we don't allow the effective value
  * to be changed.
  */
-static int __get_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
-			bool raz)
+static int __get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+			void __user *uaddr, bool raz)
 {
 	const u64 id = sys_reg_to_index(rd);
-	const u64 val = read_id_reg(rd, raz);
+	const u64 val = read_id_reg(vcpu, rd, raz);
 
 	return reg_to_user(uaddr, &val, id);
 }
 
-static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
-			bool raz)
+static int __set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+			void __user *uaddr, bool raz)
 {
 	const u64 id = sys_reg_to_index(rd);
 	int err;
@@ -1136,7 +1145,7 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
 		return err;
 
 	/* This is what we mean by invariant: you can't change it. */
-	if (val != read_id_reg(rd, raz))
+	if (val != read_id_reg(vcpu, rd, raz))
 		return -EINVAL;
 
 	return 0;
@@ -1145,25 +1154,25 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
 static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 		      const struct kvm_one_reg *reg, void __user *uaddr)
 {
-	return __get_id_reg(rd, uaddr, false);
+	return __get_id_reg(vcpu, rd, uaddr, false);
 }
 
 static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 		      const struct kvm_one_reg *reg, void __user *uaddr)
 {
-	return __set_id_reg(rd, uaddr, false);
+	return __set_id_reg(vcpu, rd, uaddr, false);
 }
 
 static int get_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 			  const struct kvm_one_reg *reg, void __user *uaddr)
 {
-	return __get_id_reg(rd, uaddr, true);
+	return __get_id_reg(vcpu, rd, uaddr, true);
 }
 
 static int set_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 			  const struct kvm_one_reg *reg, void __user *uaddr)
 {
-	return __set_id_reg(rd, uaddr, true);
+	return __set_id_reg(vcpu, rd, uaddr, true);
 }
 
 /* sys_reg_desc initialiser for known cpufeature ID registers */
-- 
2.7.4