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From: Tengfei Yu <moehanabichan@gmail.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>
Cc: Tengfei Yu <moehanabichan@gmail.com>,
	kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2] KVM: x86: Check irqchip mode before create PIT
Date: Thu, 25 Jan 2024 13:08:23 +0800
Message-Id: <20240125050823.4893-1-moehanabichan@gmail.com>
In-Reply-To: <ZbGkZlFmi1war6vq@google.com>
References: <ZbGkZlFmi1war6vq@google.com>
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MIME-Version: 1.0
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As the kvm api(https://docs.kernel.org/virt/kvm/api.html) reads,
KVM_CREATE_PIT2 call is only valid after enabling in-kernel irqchip
support via KVM_CREATE_IRQCHIP.

Without this check, I can create PIT first and enable irqchip-split
then, which may cause the PIT invalid because of lacking of in-kernel
PIC to inject the interrupt.

Signed-off-by: Tengfei Yu <moehanabichan@gmail.com>
---
v1 -> v2: Change errno from -EEXIST to -ENOENT.
v1 link: https://lore.kernel.org/lkml/ZbGkZlFmi1war6vq@google.com/

 arch/x86/kvm/x86.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 27e23714e960..c1e3aecd627f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7016,6 +7016,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		r = -EEXIST;
 		if (kvm->arch.vpit)
 			goto create_pit_unlock;
+		r = -ENOENT;
+		if (!pic_in_kernel(kvm))
+			goto create_pit_unlock;
 		r = -ENOMEM;
 		kvm->arch.vpit = kvm_create_pit(kvm, u.pit_config.flags);
 		if (kvm->arch.vpit)
-- 
2.39.3