Skip to contentSkip to conversation

KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi_exitmap()

PATCH Superseded 黄乐 2 participants 2 messages Nov 13, 2021 – Nov 15, 2021

Subsystems (3)
x86 KVM KVM x86

v1 of 2 Superseded Latest is v2 →

lore
Share & tools
lore

黄乐

author
#0 lore raw

PATCH 1/1 KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi_exitmap()

In vcpu_load_eoi_exitmap(), currently the eoi_exit_bitmap[4] array is initialized only when Hyper-V context is available, in other path it is just passed to kvm_x86_ops.load_eoi_exitmap() directly from on the stack, which would cause unexpected interrupt delivery/handling issues, e.g. an *old* linux kernel that relies on PIT to do clock calibration on KVM might randomly fail to boot.

Fix it by passing ioapic_handled_vectors to load_eoi_exitmap() when Hyper-V context is not available.

Signed-off-by Huang Le <[email protected]>

---

arch/x86/kvm/x86.c +7 -4
index dc7eb5fddfd3..0699832504c9 100644
@@ -9547,11 +9547,14 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
 	if (!kvm_apic_hw_enabled(vcpu->arch.apic))
 		return;
 
-	if (to_hv_vcpu(vcpu))
-		bitmap_or((ulong *)eoi_exit_bitmap,
-			  vcpu->arch.ioapic_handled_vectors,
-			  to_hv_synic(vcpu)->vec_bitmap, 256);
+	if (!to_hv_vcpu(vcpu)) {
+		static_call(kvm_x86_load_eoi_exitmap)(
+			vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
+		return;
+	}
 
+	bitmap_or((ulong *)eoi_exit_bitmap, vcpu->arch.ioapic_handled_vectors,
+		  to_hv_synic(vcpu)->vec_bitmap, 256);
 	static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
 }
Reviewed-by on v1 1/1
#1 lore raw
Quoted 11 lines · 黄乐

In vcpu_load_eoi_exitmap(), currently the eoi_exit_bitmap[4] array is initialized only when Hyper-V context is available, in other path it is just passed to kvm_x86_ops.load_eoi_exitmap() directly from on the stack, which would cause unexpected interrupt delivery/handling issues, e.g. an *old* linux kernel that relies on PIT to do clock calibration on KVM might randomly fail to boot.

Fix it by passing ioapic_handled_vectors to load_eoi_exitmap() when Hyper-V context is not available.

Signed-off-by Huang Le <[email protected]>
Fixes f2bc14b69c38 ("KVM: x86: hyper-v: Prepare to meet unallocated Hyper-V context")
Cc [email protected]
Quoted 14 lines

---

arch/x86/kvm/x86.c +1 -4
index dc7eb5fddfd3..0699832504c9 100644
@@ -9547,11 +9547,14 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
 	if (!kvm_apic_hw_enabled(vcpu->arch.apic))
 		return;
 
-	if (to_hv_vcpu(vcpu))
-		bitmap_or((ulong *)eoi_exit_bitmap,
-			  vcpu->arch.ioapic_handled_vectors,
-			  to_hv_synic(vcpu)->vec_bitmap, 256);
+	if (!to_hv_vcpu(vcpu)) {

arch/x86/kvm/x86.c static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu) · line 9560

Quoted 10 lines
arch/x86/kvm/x86.c +6 -0
+		static_call(kvm_x86_load_eoi_exitmap)(
+			vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
+		return;
+	}
 
+	bitmap_or((ulong *)eoi_exit_bitmap, vcpu->arch.ioapic_handled_vectors,
+		  to_hv_synic(vcpu)->vec_bitmap, 256);
 	static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
 }
Reviewed-by Vitaly Kuznetsov <[email protected]>

My personal preference, however, would be to keep 'if (to_hv_vcpu(vcpu))' check and not invert it, i.e.:

	if (to_hv_vcpu(vcpu)) {
		bitmap_or((ulong *)eoi_exit_bitmap,
                	vcpu->arch.ioapic_handled_vectors,
                	to_hv_synic(vcpu)->vec_bitmap, 256);
                static_call(...)(vcpu, eoi_exit_bitmap)
                return;
        }

	static_call(...)(vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);

to slightly reduce the code churn but it doesn't matter much.

Thanks!

Signature · 1 line
Vitaly