linux-kernel - [PATCH 01/28] KVM: SVM: Don't BUG if setting up the MSR intercept bitmaps fails

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Message-ID: <20250529234013.3826933-2-seanjc@google.com>
Date: Thu, 29 May 2025 16:39:46 -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 01/28] KVM: SVM: Don't BUG if setting up the MSR intercept
 bitmaps fails

WARN and reject module loading if there is a problem with KVM's MSR
interception bitmaps.  Panicking the host in this situation is inexcusable
since it is trivially easy to propagate the error up the stack.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 0ad1a6d4fb6d..bd75ff8e4f20 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -945,7 +945,7 @@ static void svm_msr_filter_changed(struct kvm_vcpu *vcpu)
 	}
 }
 
-static void add_msr_offset(u32 offset)
+static int add_msr_offset(u32 offset)
 {
 	int i;
 
@@ -953,7 +953,7 @@ static void add_msr_offset(u32 offset)
 
 		/* Offset already in list? */
 		if (msrpm_offsets[i] == offset)
-			return;
+			return 0;
 
 		/* Slot used by another offset? */
 		if (msrpm_offsets[i] != MSR_INVALID)
@@ -962,17 +962,13 @@ static void add_msr_offset(u32 offset)
 		/* Add offset to list */
 		msrpm_offsets[i] = offset;
 
-		return;
+		return 0;
 	}
 
-	/*
-	 * If this BUG triggers the msrpm_offsets table has an overflow. Just
-	 * increase MSRPM_OFFSETS in this case.
-	 */
-	BUG();
+	return -EIO;
 }
 
-static void init_msrpm_offsets(void)
+static int init_msrpm_offsets(void)
 {
 	int i;
 
@@ -982,10 +978,13 @@ static void init_msrpm_offsets(void)
 		u32 offset;
 
 		offset = svm_msrpm_offset(direct_access_msrs[i].index);
-		BUG_ON(offset == MSR_INVALID);
+		if (WARN_ON(offset == MSR_INVALID))
+			return -EIO;
 
-		add_msr_offset(offset);
+		if (WARN_ON_ONCE(add_msr_offset(offset)))
+			return -EIO;
 	}
+	return 0;
 }
 
 void svm_copy_lbrs(struct vmcb *to_vmcb, struct vmcb *from_vmcb)
@@ -5511,7 +5510,11 @@ static __init int svm_hardware_setup(void)
 	memset(iopm_va, 0xff, PAGE_SIZE * (1 << order));
 	iopm_base = __sme_page_pa(iopm_pages);
 
-	init_msrpm_offsets();
+	r = init_msrpm_offsets();
+	if (r) {
+		__free_pages(__sme_pa_to_page(iopm_base), get_order(IOPM_SIZE));
+		return r;
+	}
 
 	kvm_caps.supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS |
 				     XFEATURE_MASK_BNDCSR);
-- 
2.49.0.1204.g71687c7c1d-goog