From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 3 Mar 2025 14:09:37 +0000 (-0500)
Subject: KVM: x86: do not allow re-enabling quirks
X-Git-Tag: v6.16-rc1~78^2~17^2^2~7
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=9966b7822b3f49b3aea5d926ece4bc92f1f0a700;p=linux-2.6-block.git

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@redhat.com>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index df2da8b511c7..cdc9c7b96511 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6533,7 +6533,7 @@ 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: {