linux-kernel - Re: [Patch v1] KVM: x86: Initializing all kvm_lapic

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Date:   Wed, 11 Mar 2020 19:49:38 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Nitesh Narayan Lal <nitesh@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mtosatti@...hat.com,
        vkuznets@...hat.com, sean.j.christopherson@...el.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org
Subject: Re: [Patch v1] KVM: x86: Initializing all kvm_lapic_irq fields

On 11/03/20 19:34, Nitesh Narayan Lal wrote:
> Previously all fields of structure kvm_lapic_irq were not initialized
> before it was passed to kvm_bitmap_or_dest_vcpus(). Which will cause
> an issue when any of those fields are used for processing a request.
> This patch initializes all the fields of kvm_lapic_irq based on the
> values which are passed through the ioapic redirect_entry object.

Can you explain better how the bug manifests itself?

Thanks,

Paolo

> Fixes: 7ee30bc132c6("KVM: x86: deliver KVM IOAPIC scan request to target vCPUs")
> Signed-off-by: Nitesh Narayan Lal <nitesh@...hat.com>
> ---
>  arch/x86/kvm/ioapic.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> index 7668fed..3a8467d 100644
> --- a/arch/x86/kvm/ioapic.c
> +++ b/arch/x86/kvm/ioapic.c
> @@ -378,12 +378,15 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
>  		if (e->fields.delivery_mode == APIC_DM_FIXED) {
>  			struct kvm_lapic_irq irq;
>  
> -			irq.shorthand = APIC_DEST_NOSHORT;
>  			irq.vector = e->fields.vector;
>  			irq.delivery_mode = e->fields.delivery_mode << 8;
> -			irq.dest_id = e->fields.dest_id;
>  			irq.dest_mode =
>  			    kvm_lapic_irq_dest_mode(!!e->fields.dest_mode);
> +			irq.level = 1;
> +			irq.trig_mode = e->fields.trig_mode;
> +			irq.shorthand = APIC_DEST_NOSHORT;
> +			irq.dest_id = e->fields.dest_id;
> +			irq.msi_redir_hint = false;
>  			bitmap_zero(&vcpu_bitmap, 16);
>  			kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq,
>  						 &vcpu_bitmap);
>