From 966eefb8965798478c2a6de3aa35ec180323792d Mon Sep 17 00:00:00 2001 From: Jim Mattson Date: Fri, 4 Jun 2021 10:26:06 -0700 Subject: [PATCH] KVM: nVMX: Disable vmcs02 posted interrupts if vmcs12 PID isn't mappable 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 Message-Id: <20210604172611.281819-8-jmattson@google.com> Signed-off-by: Paolo Bonzini --- 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 4e545996440b..98b5f5f104da 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3184,6 +3184,15 @@ 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)) @@ -3696,10 +3705,14 @@ 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;