linux-kernel - Re: [PATCH v2] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in vcpu_load_eoi

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Message-ID: <b455d273-ef5e-bc78-ac31-2543499324b6@redhat.com>
Date:   Tue, 16 Nov 2021 10:44:17 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     黄乐 <huangle1@...com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] KVM: x86: Fix uninitialized eoi_exit_bitmap usage in
 vcpu_load_eoi_exitmap()

On 11/15/21 15:08, 黄乐 wrote:
> 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.
> 
> Fixes: f2bc14b69c38 ("KVM: x86: hyper-v: Prepare to meet unallocated Hyper-V context")
> Cc: stable@...r.kernel.org
> Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> Signed-off-by: Huang Le <huangle1@...com>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index dc7eb5fddfd3..26466f94e31a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9547,12 +9547,16 @@ static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
>   	if (!kvm_apic_hw_enabled(vcpu->arch.apic))
>   		return;
>   
> -	if (to_hv_vcpu(vcpu))
> +	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(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
> +		return;
> +	}
>   
> -	static_call(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
> +	static_call(kvm_x86_load_eoi_exitmap)(
> +		vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
>   }
>   
>   void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
> 

Queued, thanks.

Paolo