KVM: arm64: Reject ioctl access to FPSIMD V-regs on SVE vcpus

In order to avoid the pointless complexity of maintaining two ioctl
register access views of the same data, this patch blocks ioctl
access to the FPSIMD V-registers on vcpus that support SVE.

This will make it more straightforward to add SVE register access
support.

Since SVE is an opt-in feature for userspace, this will not affect
existing users.
Signed-off-by: NDave Martin <Dave.Martin@arm.com>
Reviewed-by: NJulien Thierry <julien.thierry@arm.com>
Tested-by: Nzhang.lei <zhang.lei@jp.fujitsu.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/guest.c

@@ -54,12 +54,19 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+static bool core_reg_offset_is_vreg(u64 off)
+{
+	return off >= KVM_REG_ARM_CORE_REG(fp_regs.vregs) &&
+		off < KVM_REG_ARM_CORE_REG(fp_regs.fpsr);
+}
+
 static u64 core_reg_offset_from_id(u64 id)
 {
 	return id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK | KVM_REG_ARM_CORE);
 }
 
-static int validate_core_offset(const struct kvm_one_reg *reg)
+static int validate_core_offset(const struct kvm_vcpu *vcpu,
+				const struct kvm_one_reg *reg)
 {
 	u64 off = core_reg_offset_from_id(reg->id);
 	int size;
@@ -91,11 +98,19 @@ static int validate_core_offset(const struct kvm_one_reg *reg)
 		return -EINVAL;
 	}
 
-	if (KVM_REG_SIZE(reg->id) == size &&
-	    IS_ALIGNED(off, size / sizeof(__u32)))
-		return 0;
+	if (KVM_REG_SIZE(reg->id) != size ||
+	    !IS_ALIGNED(off, size / sizeof(__u32)))
+		return -EINVAL;
 
-	return -EINVAL;
+	/*
+	 * The KVM_REG_ARM64_SVE regs must be used instead of
+	 * KVM_REG_ARM_CORE for accessing the FPSIMD V-registers on
+	 * SVE-enabled vcpus:
+	 */
+	if (vcpu_has_sve(vcpu) && core_reg_offset_is_vreg(off))
+		return -EINVAL;
+
+	return 0;
 }
 
 static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
@@ -117,7 +132,7 @@ static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	    (off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs)
 		return -ENOENT;
 
-	if (validate_core_offset(reg))
+	if (validate_core_offset(vcpu, reg))
 		return -EINVAL;
 
 	if (copy_to_user(uaddr, ((u32 *)regs) + off, KVM_REG_SIZE(reg->id)))
@@ -142,7 +157,7 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	    (off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs)
 		return -ENOENT;
 
-	if (validate_core_offset(reg))
+	if (validate_core_offset(vcpu, reg))
 		return -EINVAL;
 
 	if (KVM_REG_SIZE(reg->id) > sizeof(tmp))
@@ -195,13 +210,22 @@ int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 	return -EINVAL;
 }
 
-static int kvm_arm_copy_core_reg_indices(u64 __user *uindices)
+static int copy_core_reg_indices(const struct kvm_vcpu *vcpu,
+				 u64 __user *uindices)
 {
 	unsigned int i;
 	int n = 0;
 	const u64 core_reg = KVM_REG_ARM64 | KVM_REG_SIZE_U64 | KVM_REG_ARM_CORE;
 
 	for (i = 0; i < sizeof(struct kvm_regs) / sizeof(__u32); i++) {
+		/*
+		 * The KVM_REG_ARM64_SVE regs must be used instead of
+		 * KVM_REG_ARM_CORE for accessing the FPSIMD V-registers on
+		 * SVE-enabled vcpus:
+		 */
+		if (vcpu_has_sve(vcpu) && core_reg_offset_is_vreg(i))
+			continue;
+
 		if (uindices) {
 			if (put_user(core_reg | i, uindices))
 				return -EFAULT;
@@ -214,9 +238,9 @@ static int kvm_arm_copy_core_reg_indices(u64 __user *uindices)
 	return n;
 }
 
-static unsigned long num_core_regs(void)
+static unsigned long num_core_regs(const struct kvm_vcpu *vcpu)
 {
-	return kvm_arm_copy_core_reg_indices(NULL);
+	return copy_core_reg_indices(vcpu, NULL);
 }
 
 /**
@@ -281,7 +305,7 @@ unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
 {
 	unsigned long res = 0;
 
-	res += num_core_regs();
+	res += num_core_regs(vcpu);
 	res += kvm_arm_num_sys_reg_descs(vcpu);
 	res += kvm_arm_get_fw_num_regs(vcpu);
 	res += NUM_TIMER_REGS;
@@ -298,7 +322,7 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 {
 	int ret;
 
-	ret = kvm_arm_copy_core_reg_indices(uindices);
+	ret = copy_core_reg_indices(vcpu, uindices);
 	if (ret)
 		return ret;
 	uindices += ret;