linux-kernel - [PATCH v3 1/6] KVM: x86: do not allow re-enabling quirks

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Message-ID: <20250304060647.2903469-2-pbonzini@redhat.com>
Date: Tue,  4 Mar 2025 01:06:42 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: xiaoyao.li@...el.com,
	seanjc@...gle.com,
	yan.y.zhao@...el.com
Subject: [PATCH v3 1/6] KVM: x86: do not allow re-enabling quirks

Allowing arbitrary re-enabling of quirks puts a limit on what the
quirks themselves can do, since you cannot assume that the quirk
prevents a particular state.  More important, it also prevents
KVM from disabling a quirk at VM creation time, because userspace
can always go back and re-enable that.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 856ceeb4fb35..35d03fcdb8e9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6525,7 +6525,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 			break;
 		fallthrough;
 	case KVM_CAP_DISABLE_QUIRKS:
-		kvm->arch.disabled_quirks = cap->args[0];
+		kvm->arch.disabled_quirks |= cap->args[0];
 		r = 0;
 		break;
 	case KVM_CAP_SPLIT_IRQCHIP: {
-- 
2.43.5