linux-kernel - [PATCH 04/28] KVM: SVM: Kill the VM instead of the host if MSR interception is buggy

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Message-ID: <20250529234013.3826933-5-seanjc@google.com>
Date: Thu, 29 May 2025 16:39:49 -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, 
	Borislav Petkov <bp@...en8.de>, Xin Li <xin@...or.com>, Chao Gao <chao.gao@...el.com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [PATCH 04/28] KVM: SVM: Kill the VM instead of the host if MSR
 interception is buggy

WARN and kill the VM instead of panicking the host if KVM attempts to set
or query MSR interception for an unsupported MSR.  Accessing the MSR
interception bitmaps only meaningfully affects post-VMRUN behavior, and
KVM_BUG_ON() is guaranteed to prevent the current vCPU from doing VMRUN,
i.e. there is no need to panic the entire host.

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

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 36a99b87a47f..d5d11cb0c987 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -827,7 +827,8 @@ static bool msr_write_intercepted(struct kvm_vcpu *vcpu, u32 msr)
 	bit_write = 2 * (msr & 0x0f) + 1;
 	tmp       = msrpm[offset];
 
-	BUG_ON(offset == MSR_INVALID);
+	if (KVM_BUG_ON(offset == MSR_INVALID, vcpu->kvm))
+		return false;
 
 	return test_bit(bit_write, &tmp);
 }
@@ -858,7 +859,8 @@ static void set_msr_interception_bitmap(struct kvm_vcpu *vcpu, u32 *msrpm,
 	bit_write = 2 * (msr & 0x0f) + 1;
 	tmp       = msrpm[offset];
 
-	BUG_ON(offset == MSR_INVALID);
+	if (KVM_BUG_ON(offset == MSR_INVALID, vcpu->kvm))
+		return;
 
 	read  ? clear_bit(bit_read,  &tmp) : set_bit(bit_read,  &tmp);
 	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
-- 
2.49.0.1204.g71687c7c1d-goog