linux-kernel - [PATCH 2/4] KVM: x86: WARN and reject KVM_RUN if vCPU's MP_STATE is SIPI

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Message-ID: <20250605195018.539901-3-seanjc@google.com>
Date: Thu,  5 Jun 2025 12:50:16 -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, 
	syzbot+c1cbaedc2613058d5194@...kaller.appspotmail.com
Subject: [PATCH 2/4] KVM: x86: WARN and reject KVM_RUN if vCPU's MP_STATE is SIPI_RECEIVED

WARN if KVM_RUN is reached with a vCPU's mp_state set to SIPI_RECEIVED, as
KVM no longer uses SIPI_RECEIVED internally, and should morph SIPI_RECEIVED
into INIT_RECEIVED with a pending SIPI if userspace forces SIPI_RECEIVED.

See commit 66450a21f996 ("KVM: x86: Rework INIT and SIPI handling") for
more history and details.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7e3ab297a1bf..c3cbcd9e39f6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11547,6 +11547,20 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
 	trace_kvm_fpu(0);
 }
 
+static int kvm_x86_vcpu_pre_run(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * SIPI_RECEIVED is obsolete; KVM leaves the vCPU in Wait-For-SIPI and
+	 * tracks the pending SIPI separately.  SIPI_RECEIVED is still accepted
+	 * by KVM_SET_VCPU_EVENTS for backwards compatibility, but should be
+	 * converted to INIT_RECEIVED.
+	 */
+	if (WARN_ON_ONCE(vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED))
+		return -EINVAL;
+
+	return kvm_x86_call(vcpu_pre_run)(vcpu);
+}
+
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
 	struct kvm_queued_exception *ex = &vcpu->arch.exception;
@@ -11649,7 +11663,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		goto out;
 	}
 
-	r = kvm_x86_call(vcpu_pre_run)(vcpu);
+	r = kvm_x86_vcpu_pre_run(vcpu);
 	if (r <= 0)
 		goto out;
 
-- 
2.50.0.rc0.604.gd4ff7b7c86-goog