KVM: arm/arm64: Allow user injection of external data aborts

In some scenarios, such as buggy guest or incorrect configuration of the
VMM and firmware description data, userspace will detect a memory access
to a portion of the IPA, which is not mapped to any MMIO region.

For this purpose, the appropriate action is to inject an external abort
to the guest.  The kernel already has functionality to inject an
external abort, but we need to wire up a signal from user space that
lets user space tell the kernel to do this.

It turns out, we already have the set event functionality which we can
perfectly reuse for this.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

5 files changed, 26 insertions, 4 deletions

diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index 2769360f195c..03cd7c19a683 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -131,8 +131,9 @@ struct kvm_vcpu_events {
 	struct {
 		__u8 serror_pending;
 		__u8 serror_has_esr;
+		__u8 ext_dabt_pending;
 		/* Align it to 8 bytes */
-		__u8 pad[6];
+		__u8 pad[5];
 		__u64 serror_esr;
 	} exception;
 	__u32 reserved[12];
diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
index 684cf64b4033..735f9b007e58 100644
--- a/arch/arm/kvm/guest.c
+++ b/arch/arm/kvm/guest.c
@@ -255,6 +255,12 @@ int __kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
 {
 	events->exception.serror_pending = !!(*vcpu_hcr(vcpu) & HCR_VA);
 
+	/*
+	 * We never return a pending ext_dabt here because we deliver it to
+	 * the virtual CPU directly when setting the event and it's no longer
+	 * 'pending' at this point.
+	 */
+
 	return 0;
 }
 
@@ -263,12 +269,16 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 {
 	bool serror_pending = events->exception.serror_pending;
 	bool has_esr = events->exception.serror_has_esr;
+	bool ext_dabt_pending = events->exception.ext_dabt_pending;
 
 	if (serror_pending && has_esr)
 		return -EINVAL;
 	else if (serror_pending)
 		kvm_inject_vabt(vcpu);
 
+	if (ext_dabt_pending)
+		kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
+
 	return 0;
 }
 
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 67c21f9bdbad..d49c17a80491 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -164,8 +164,9 @@ struct kvm_vcpu_events {
 	struct {
 		__u8 serror_pending;
 		__u8 serror_has_esr;
+		__u8 ext_dabt_pending;
 		/* Align it to 8 bytes */
-		__u8 pad[6];
+		__u8 pad[5];
 		__u64 serror_esr;
 	} exception;
 	__u32 reserved[12];
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index dfd626447482..ca613a44c6ec 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -712,6 +712,12 @@ int __kvm_arm_vcpu_get_events(struct kvm_vcpu *vcpu,
 	if (events->exception.serror_pending && events->exception.serror_has_esr)
 		events->exception.serror_esr = vcpu_get_vsesr(vcpu);
 
+	/*
+	 * We never return a pending ext_dabt here because we deliver it to
+	 * the virtual CPU directly when setting the event and it's no longer
+	 * 'pending' at this point.
+	 */
+
 	return 0;
 }
 
@@ -720,6 +726,7 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 {
 	bool serror_pending = events->exception.serror_pending;
 	bool has_esr = events->exception.serror_has_esr;
+	bool ext_dabt_pending = events->exception.ext_dabt_pending;
 
 	if (serror_pending && has_esr) {
 		if (!cpus_have_const_cap(ARM64_HAS_RAS_EXTN))
@@ -733,6 +740,9 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
 		kvm_inject_vabt(vcpu);
 	}
 
+	if (ext_dabt_pending)
+		kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
+
 	return 0;
 }
 
diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
index a9d25a305af5..ccdb6a051ab2 100644
--- a/arch/arm64/kvm/inject_fault.c
+++ b/arch/arm64/kvm/inject_fault.c
@@ -109,7 +109,7 @@ static void inject_undef64(struct kvm_vcpu *vcpu)
 
 /**
  * kvm_inject_dabt - inject a data abort into the guest
- * @vcpu: The VCPU to receive the undefined exception
+ * @vcpu: The VCPU to receive the data abort
  * @addr: The address to report in the DFAR
  *
  * It is assumed that this code is called from the VCPU thread and that the
@@ -125,7 +125,7 @@ void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
 
 /**
  * kvm_inject_pabt - inject a prefetch abort into the guest
- * @vcpu: The VCPU to receive the undefined exception
+ * @vcpu: The VCPU to receive the prefetch abort
  * @addr: The address to report in the DFAR
  *
  * It is assumed that this code is called from the VCPU thread and that the