Don't allow posted interrupts to modify a stale posted interrupt
descriptor (including the initial value of 0).
Empirical tests on real hardware reveal that a posted interrupt
descriptor referencing an unbacked address has PCI bus error semantics
(reads as all 1's; writes are ignored). However, kvm can't distinguish
unbacked addresses from device-backed (MMIO) addresses, so it should
really ask userspace for an MMIO completion. That's overly
complicated, so just punt with KVM_INTERNAL_ERROR.
Don't return the error until the posted interrupt descriptor is
actually accessed. We don't want to break the existing kvm-unit-tests
that assume they can launch an L2 VM with a posted interrupt
descriptor that references MMIO space in L1.
Fixes: 6beb7bd52e48 ("kvm: nVMX: Refactor nested_get_vmcs12_pages()")
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 706c31821362..632f0abfe154 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3175,6 +3175,15 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
offset_in_page(vmcs12->posted_intr_desc_addr));
vmcs_write64(POSTED_INTR_DESC_ADDR,
pfn_to_hpa(map->pfn) + offset_in_page(vmcs12->posted_intr_desc_addr));
+ } else {
+ /*
+ * Defer the KVM_INTERNAL_EXIT until KVM tries to
+ * access the contents of the VMCS12 posted interrupt
+ * descriptor. (Note that KVM may do this when it
+ * should not, per the architectural specification.)
+ */
+ vmx->nested.pi_desc = NULL;
+ pin_controls_clearbit(vmx, PIN_BASED_POSTED_INTR);
}
}
if (nested_vmx_prepare_msr_bitmap(vcpu, vmcs12))
@@ -3689,10 +3698,14 @@ static int vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
void *vapic_page;
u16 status;
- if (!vmx->nested.pi_desc || !vmx->nested.pi_pending)
+ if (!vmx->nested.pi_pending)
return 0;
+ if (!vmx->nested.pi_desc)
+ goto mmio_needed;
+
vmx->nested.pi_pending = false;
+
if (!pi_test_and_clear_on(vmx->nested.pi_desc))
return 0;
--
2.32.0.rc1.229.g3e70b5a671-goog
