[PATCH 1/2] KVM: VMX: Disable posted interrupts for odd IRQs

[Alexander Graf <graf@amazon.com>]

We can easily route hardware interrupts directly into VM context when
they target the "Fixed" or "LowPriority" delivery modes.

However, on modes such as "SMI" or "Init", we need to go via KVM code
to actually put the vCPU into a different mode of operation, so we can
not post the interrupt

Add code in the VMX PI logic to explicitly refuse to establish posted
mappings for advanced IRQ deliver modes.

This fixes a bug I have with code which configures real hardware to
inject virtual SMIs into my guest.

Signed-off-by: Alexander Graf <graf@amazon.com>
---
 arch/x86/kvm/vmx/vmx.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 570a233e272b..d16c4ae8f685 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7401,6 +7401,28 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
 			continue;
 		}
 
+		switch (irq.delivery_mode) {
+		case dest_Fixed:
+		case dest_LowestPrio:
+			break;
+		default:
+			/*
+			 * For non-trivial interrupt events, we need to go
+			 * through the full KVM IRQ code, so refuse to take
+			 * any direct PI assignments here.
+			 */
+
+			ret = irq_set_vcpu_affinity(host_irq, NULL);
+			if (ret < 0) {
+				printk(KERN_INFO
+				   "failed to back to remapped mode, irq: %u\n",
+				   host_irq);
+				goto out;
+			}
+
+			continue;
+		}
+
 		vcpu_info.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu));
 		vcpu_info.vector = irq.vector;
 
-- 
2.17.1




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