KVM: arm64: Route SEAs to the SError vector when EASE is set

One of the finest additions of FEAT_DoubleFault2 is the ability for
software to request *synchronous* external aborts be taken to the
SError vector, which of coure are *asynchronous* in nature.

Opinions be damned, implement the architecture and send SEAs to the
SError vector if EASE is set for the target context.

Reviewed-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Oliver Upton <[email protected]>

Author: oupton

arch/arm64/kvm/emulate-nested.c

@@ -2834,6 +2834,10 @@ int kvm_inject_nested_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr)
 	esr |= ESR_ELx_FSC_EXTABT | ESR_ELx_IL;
 
 	vcpu_write_sys_reg(vcpu, FAR_EL2, addr);
+
+	if (__vcpu_sys_reg(vcpu, SCTLR2_EL2) & SCTLR2_EL1_EASE)
+		return kvm_inject_nested(vcpu, esr, except_type_serror);
+
 	return kvm_inject_nested_sync(vcpu, esr);
 }
 

arch/arm64/kvm/hyp/exception.c

@@ -339,6 +339,10 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu)
 			enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);
 			break;
 
+		case unpack_vcpu_flag(EXCEPT_AA64_EL1_SERR):
+			enter_exception64(vcpu, PSR_MODE_EL1h, except_type_serror);
+			break;
+
 		case unpack_vcpu_flag(EXCEPT_AA64_EL2_SYNC):
 			enter_exception64(vcpu, PSR_MODE_EL2h, except_type_sync);
 			break;
@@ -353,7 +357,7 @@ static void kvm_inject_exception(struct kvm_vcpu *vcpu)
 
 		default:
 			/*
-			 * Only EL1_SYNC and EL2_{SYNC,IRQ,SERR} makes
+			 * Only EL1_{SYNC,SERR} and EL2_{SYNC,IRQ,SERR} makes
 			 * sense so far. Everything else gets silently
 			 * ignored.
 			 */

arch/arm64/kvm/inject_fault.c

@@ -65,13 +65,49 @@ static void pend_sync_exception(struct kvm_vcpu *vcpu)
 		kvm_pend_exception(vcpu, EXCEPT_AA64_EL2_SYNC);
 }
 
+static void pend_serror_exception(struct kvm_vcpu *vcpu)
+{
+	if (exception_target_el(vcpu) == PSR_MODE_EL1h)
+		kvm_pend_exception(vcpu, EXCEPT_AA64_EL1_SERR);
+	else
+		kvm_pend_exception(vcpu, EXCEPT_AA64_EL2_SERR);
+}
+
+static bool __effective_sctlr2_bit(struct kvm_vcpu *vcpu, unsigned int idx)
+{
+	u64 sctlr2;
+
+	if (!kvm_has_sctlr2(vcpu->kvm))
+		return false;
+
+	if (is_nested_ctxt(vcpu) &&
+	    !(__vcpu_sys_reg(vcpu, HCRX_EL2) & HCRX_EL2_SCTLR2En))
+		return false;
+
+	if (exception_target_el(vcpu) == PSR_MODE_EL1h)
+		sctlr2 = vcpu_read_sys_reg(vcpu, SCTLR2_EL1);
+	else
+		sctlr2 = vcpu_read_sys_reg(vcpu, SCTLR2_EL2);
+
+	return sctlr2 & BIT(idx);
+}
+
+static bool effective_sctlr2_ease(struct kvm_vcpu *vcpu)
+{
+	return __effective_sctlr2_bit(vcpu, SCTLR2_EL1_EASE_SHIFT);
+}
+
 static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr)
 {
 	unsigned long cpsr = *vcpu_cpsr(vcpu);
 	bool is_aarch32 = vcpu_mode_is_32bit(vcpu);
 	u64 esr = 0;
 
-	pend_sync_exception(vcpu);
+	/* This delight is brought to you by FEAT_DoubleFault2. */
+	if (effective_sctlr2_ease(vcpu))
+		pend_serror_exception(vcpu);
+	else
+		pend_sync_exception(vcpu);
 
 	/*
 	 * Build an {i,d}abort, depending on the level and the