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Date: Fri, 6 Jun 2014 15:12:00 +0200
From: Cornelia Huck <cornelia.huck@de.ibm.com>
Message-ID: <20140606151200.660e3072.cornelia.huck@de.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH] KVM: Fix GSI number space limit
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To: Alexander Graf <agraf@suse.de>
Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org

On Fri,  6 Jun 2014 14:46:05 +0200
Alexander Graf <agraf@suse.de> wrote:

> KVM tells us the number of GSIs it can handle inside the kernel. That value is
> basically KVM_MAX_IRQ_ROUTES. However when we try to set the GSI mapping table,
> it checks for
> 
>     r = -EINVAL;
>     if (routing.nr >= KVM_MAX_IRQ_ROUTES)
>         goto out;
> 
> erroring out even when we're only using all of the GSIs. To make sure we never
> hit that limit, let's reduce the number of GSIs we get from KVM by one.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  kvm-all.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index 4e19eff..56a251b 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -938,7 +938,7 @@ void kvm_init_irq_routing(KVMState *s)
>  {
>      int gsi_count, i;
> 
> -    gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING);
> +    gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1;
>      if (gsi_count > 0) {
>          unsigned int gsi_bits, i;
> 

But gsi_count is already marked as used further down in this function,
isn't it? Confused.