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From: Jim Mattson <jmattson@google.com>
To: kvm@vger.kernel.org, pbonzini@redhat.com
Cc: Jim Mattson <jmattson@google.com>
Subject: [PATCH 07/12] KVM: nVMX: Disable vmcs02 posted interrupts if vmcs12 PID isn't mappable
Date: Thu, 20 May 2021 16:03:34 -0700	[thread overview]
Message-ID: <20210520230339.267445-8-jmattson@google.com> (raw)
In-Reply-To: <20210520230339.267445-1-jmattson@google.com>

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@google.com>
---
 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..defd42201bb4 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_ERROR exit until
+			 * someone tries to trigger posted interrupt
+			 * processing on this vCPU, to avoid breaking
+			 * existing kvm-unit-tests.
+			 */
+			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;
 
-- 
2.31.1.818.g46aad6cb9e-goog


  parent reply	other threads:[~2021-05-20 23:04 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-20 23:03 [PATCH 00/12] KVM: nVMX: Fix vmcs02 PID use-after-free issue Jim Mattson
2021-05-20 23:03 ` [PATCH 01/12] KVM: x86: Remove guest mode check from kvm_check_nested_events Jim Mattson
2021-05-20 23:03 ` [PATCH 02/12] KVM: x86: Wake up a vCPU when kvm_check_nested_events fails Jim Mattson
2021-05-24 15:43   ` Paolo Bonzini
2021-05-24 16:39     ` Jim Mattson
2021-05-24 16:43       ` Paolo Bonzini
2021-05-24 17:10         ` Jim Mattson
2021-05-24 23:10         ` Sean Christopherson
2021-05-24 23:23           ` Jim Mattson
2021-05-24 23:24             ` Sean Christopherson
2021-05-24 23:29               ` Jim Mattson
2021-05-24 23:34                 ` Sean Christopherson
2021-05-20 23:03 ` [PATCH 03/12] KVM: nVMX: Add a return code to vmx_complete_nested_posted_interrupt Jim Mattson
2021-05-20 23:03 ` [PATCH 04/12] KVM: x86: Add a return code to inject_pending_event Jim Mattson
2021-05-20 23:03 ` [PATCH 05/12] KVM: x86: Add a return code to kvm_apic_accept_events Jim Mattson
2021-05-25 19:24   ` Reiji Watanabe
2021-05-25 20:35     ` Jim Mattson
2021-05-20 23:03 ` [PATCH 06/12] KVM: nVMX: Fail on MMIO completion for nested posted interrupts Jim Mattson
2021-05-20 23:03 ` Jim Mattson [this message]
2021-05-24 23:21   ` [PATCH 07/12] KVM: nVMX: Disable vmcs02 posted interrupts if vmcs12 PID isn't mappable Sean Christopherson
2021-05-24 23:27     ` Jim Mattson
2021-05-24 23:45       ` Sean Christopherson
2021-05-25  0:03         ` Jim Mattson
2021-05-25  0:11           ` Sean Christopherson
2021-05-25  0:15             ` Jim Mattson
2021-05-25  0:57               ` Sean Christopherson
2021-05-20 23:03 ` [PATCH 08/12] KVM: selftests: Move APIC definitions into a separate file Jim Mattson
2021-05-20 23:03 ` [PATCH 09/12] KVM: selftests: Hoist APIC functions out of individual tests Jim Mattson
2021-05-20 23:03 ` [PATCH 10/12] KVM: selftests: Introduce x2APIC register manipulation functions Jim Mattson
2021-05-20 23:03 ` [PATCH 11/12] KVM: selftests: Introduce prepare_tpr_shadow Jim Mattson
2021-05-20 23:03 ` [PATCH 12/12] KVM: selftests: Add a test of an unbacked nested PI descriptor Jim Mattson
2021-05-21  0:58 ` [PATCH 00/12] KVM: nVMX: Fix vmcs02 PID use-after-free issue Sean Christopherson
2021-05-21 12:04 ` Jim Mattson
2021-05-24 15:50 ` Paolo Bonzini
2021-05-24 16:46 ` Paolo Bonzini

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