[PATCH 1/2] KVM: PPC: Book3S: Don't crash if irqfd used with no in-kernel XICS emulation

[PATCH 1/2] KVM: PPC: Book3S: Don't crash if irqfd used with no in-kernel XICS emulation

[Paul Mackerras]

It turns out that if userspace creates a pseries-type VM without
in-kernel XICS (interrupt controller) emulation, and then connects
an eventfd to the VM as an irqfd, and the eventfd gets signalled,
that the code will try to deliver an interrupt via the non-existent
XICS object and crash the host kernel with a NULL pointer dereference.

To fix this, we check for the presence of the XICS object before
trying to deliver the interrupt, and return with an error if not.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
---
 arch/powerpc/kvm/book3s_xics.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c
index a75ba38..d5de902 100644
--- a/arch/powerpc/kvm/book3s_xics.c
+++ b/arch/powerpc/kvm/book3s_xics.c
@@ -1252,6 +1252,8 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level,
 {
 	struct kvmppc_xics *xics = kvm->arch.xics;
 
+	if (!xics)
+		return -ENODEV;
 	return ics_deliver_irq(xics, irq, level);
 }
 
-- 
2.8.1

[PATCH 2/2] KVM: PPC: Implement kvm_arch_intc_initialized() for PPC

[Paul Mackerras]

It doesn't make sense to create irqfds for a VM that doesn't have
in-kernel interrupt controller emulation.  There is an existing
interface for architecture code to tell the irqfd code whether or
not any interrupt controller has been initialized, called
kvm_arch_intc_initialized(), so let's implement that for powerpc.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
---
 arch/powerpc/include/asm/kvm_host.h |  2 ++
 arch/powerpc/kvm/powerpc.c          | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index ec35af3..e36ce0c 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -43,6 +43,8 @@
 #include <asm/cputhreads.h>
 #define KVM_MAX_VCPU_ID                (threads_per_subcore * KVM_MAX_VCORES)
 
+#define __KVM_HAVE_ARCH_INTC_INITIALIZED
+
 #ifdef CONFIG_KVM_MMIO
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
 #endif
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 6ce40dd..ab2b3d5 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -1167,6 +1167,19 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 	return r;
 }
 
+bool kvm_arch_intc_initialized(struct kvm *kvm)
+{
+#ifdef CONFIG_KVM_MPIC
+	if (kvm->arch.mpic)
+		return true;
+#endif
+#ifdef CONFIG_KVM_XICS
+	if (kvm->arch.xics)
+		return true;
+#endif
+	return false;
+}
+
 int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
                                     struct kvm_mp_state *mp_state)
 {
-- 
2.8.1