linux-kernel - [PATCH v2 1/2] KVM: VMX: Disable posted interrupts for odd IRQs

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Message-ID: <20190904133511.17540-2-graf@amazon.com>
Date:   Wed, 4 Sep 2019 15:35:10 +0200
From:   Alexander Graf <graf@...zon.com>
To:     <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Sean Christopherson" <sean.j.christopherson@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: [PATCH v2 1/2] KVM: VMX: Disable posted interrupts for odd IRQs

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 reflects the logic in
__apic_accept_irq() which also only ever passes Fixed and LowPriority
interrupts as posted interrupts into the guest.

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@...zon.com>
Reviewed-by: Liran Alon <liran.alon@...cle.com>

---

v1 -> v2:

  - Make error message more unique
  - Update commit message to point to __apic_accept_irq()
---
 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..8029fe658c30 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
+				    "non-std IRQ failed to recover, 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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