KVM: arm64: Move existing feature disabling over to FGU infrastructure

We already trap a bunch of existing features for the purpose of
disabling them (MAIR2, POR, ACCDATA, SME...).

Let's move them over to our brand new FGU infrastructure.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240214131827.2856277-20-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: Marc Zyngier

arch/arm64/include/asm/kvm_host.h

@@ -297,6 +297,8 @@ struct kvm_arch {
 #define KVM_ARCH_FLAG_TIMER_PPIS_IMMUTABLE		6
 	/* Initial ID reg values loaded */
 #define KVM_ARCH_FLAG_ID_REGS_INITIALIZED		7
+	/* Fine-Grained UNDEF initialised */
+#define KVM_ARCH_FLAG_FGU_INITIALIZED			8
 	unsigned long flags;
 
 	/* VM-wide vCPU feature set */
@@ -1107,6 +1109,8 @@ int __init populate_nv_trap_config(void);
 bool lock_all_vcpus(struct kvm *kvm);
 void unlock_all_vcpus(struct kvm *kvm);
 
+void kvm_init_sysreg(struct kvm_vcpu *);
+
 /* MMIO helpers */
 void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data);
 unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len);

arch/arm64/kvm/arm.c

@@ -675,6 +675,12 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
 			return ret;
 	}
 
+	/*
+	 * This needs to happen after NV has imposed its own restrictions on
+	 * the feature set
+	 */
+	kvm_init_sysreg(vcpu);
+
 	ret = kvm_timer_enable(vcpu);
 	if (ret)
 		return ret;

arch/arm64/kvm/hyp/include/hyp/switch.h

@@ -157,7 +157,7 @@ static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
 	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
-	u64 r_clr = 0, w_clr = 0, r_set = 0, w_set = 0, tmp;
+	u64 r_clr = 0, w_clr = 0, r_set = 0, w_set = 0;
 	u64 r_val, w_val;
 
 	CHECK_FGT_MASKS(HFGRTR_EL2);
@@ -174,13 +174,6 @@ static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 	ctxt_sys_reg(hctxt, HFGRTR_EL2) = read_sysreg_s(SYS_HFGRTR_EL2);
 	ctxt_sys_reg(hctxt, HFGWTR_EL2) = read_sysreg_s(SYS_HFGWTR_EL2);
 
-	if (cpus_have_final_cap(ARM64_SME)) {
-		tmp = HFGxTR_EL2_nSMPRI_EL1_MASK | HFGxTR_EL2_nTPIDR2_EL0_MASK;
-
-		r_clr |= tmp;
-		w_clr |= tmp;
-	}
-
 	/*
 	 * Trap guest writes to TCR_EL1 to prevent it from enabling HA or HD.
 	 */
@@ -195,15 +188,11 @@ static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
 	compute_undef_clr_set(vcpu, kvm, HFGRTR_EL2, r_clr, r_set);
 	compute_undef_clr_set(vcpu, kvm, HFGWTR_EL2, w_clr, w_set);
 
-	/* The default to trap everything not handled or supported in KVM. */
-	tmp = HFGxTR_EL2_nAMAIR2_EL1 | HFGxTR_EL2_nMAIR2_EL1 | HFGxTR_EL2_nS2POR_EL1 |
-	      HFGxTR_EL2_nPOR_EL1 | HFGxTR_EL2_nPOR_EL0 | HFGxTR_EL2_nACCDATA_EL1;
-
-	r_val = __HFGRTR_EL2_nMASK & ~tmp;
+	r_val = __HFGRTR_EL2_nMASK;
 	r_val |= r_set;
 	r_val &= ~r_clr;
 
-	w_val = __HFGWTR_EL2_nMASK & ~tmp;
+	w_val = __HFGWTR_EL2_nMASK;
 	w_val |= w_set;
 	w_val &= ~w_clr;
 

arch/arm64/kvm/sys_regs.c

@@ -3942,6 +3942,29 @@ int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm, struct reg_mask_range *
 	return 0;
 }
 
+void kvm_init_sysreg(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+
+	mutex_lock(&kvm->arch.config_lock);
+
+	if (test_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags))
+		goto out;
+
+	kvm->arch.fgu[HFGxTR_GROUP] = (HFGxTR_EL2_nAMAIR2_EL1		|
+				       HFGxTR_EL2_nMAIR2_EL1		|
+				       HFGxTR_EL2_nS2POR_EL1		|
+				       HFGxTR_EL2_nPOR_EL1		|
+				       HFGxTR_EL2_nPOR_EL0		|
+				       HFGxTR_EL2_nACCDATA_EL1		|
+				       HFGxTR_EL2_nSMPRI_EL1_MASK	|
+				       HFGxTR_EL2_nTPIDR2_EL0_MASK);
+
+	set_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags);
+out:
+	mutex_unlock(&kvm->arch.config_lock);
+}
+
 int __init kvm_sys_reg_table_init(void)
 {
 	struct sys_reg_params params;