linux-kernel - [PATCH 5/6] KVM: nVMX: Explicitly invalidate posted_intr

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Message-ID: <20240720000138.3027780-6-seanjc@google.com>
Date: Fri, 19 Jul 2024 17:01:37 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Chao Gao <chao.gao@...el.com>, Zeng Guang <guang.zeng@...el.com>
Subject: [PATCH 5/6] KVM: nVMX: Explicitly invalidate posted_intr_nv if PI is
 disabled at VM-Enter

Explicitly set posted_intr_nv to -1 when emulating nested VM-Enter and
posted interrupts are disabled to make it clear that posted_intr_nv is
valid if and only if nested posted interrupts are enabled, and as a cheap
way to harden against KVM bugs.

Note, KVM initializes posted_intr_nv to -1 at vCPU creation and when
resets it to -1 when unloading vmcs12 and/or leaving nested mode, i.e.
this is not a bug fix (or at least, it's not intended to be a bug fix).

Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/nested.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 7e0a944088eb..40cf4839ca47 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2317,10 +2317,12 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct loaded_vmcs *vmcs0
 
 	/* Posted interrupts setting is only taken from vmcs12.  */
 	vmx->nested.pi_pending = false;
-	if (nested_cpu_has_posted_intr(vmcs12))
+	if (nested_cpu_has_posted_intr(vmcs12)) {
 		vmx->nested.posted_intr_nv = vmcs12->posted_intr_nv;
-	else
+	} else {
+		vmx->nested.posted_intr_nv = -1;
 		exec_control &= ~PIN_BASED_POSTED_INTR;
+	}
 	pin_controls_set(vmx, exec_control);
 
 	/*
-- 
2.45.2.1089.g2a221341d9-goog