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

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Message-ID: <Z8fC+T5xvUhBKYbZ@yzhao56-desk.sh.intel.com>
Date: Wed, 5 Mar 2025 11:20:25 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<xiaoyao.li@...el.com>, <seanjc@...gle.com>
Subject: Re: [PATCH v3 1/6] KVM: x86: do not allow re-enabling quirks

LGTM.

On Tue, Mar 04, 2025 at 01:06:42AM -0500, Paolo Bonzini wrote:
> 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
> 
>