Re: [Xen-devel] [PATCH v7 23/32] xen/x86: make sure the HVM callback vector is correctly set

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/10/15 16:48, Roger Pau Monne wrote:
> If certain devices (like the local or the io apic) are disabled some modes
> of operation of the HVM event channel callback cannot be used. Make sure Xen
> doesn't try to setup them.
>
> Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
>  xen/arch/x86/hvm/irq.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/xen/arch/x86/hvm/irq.c b/xen/arch/x86/hvm/irq.c
> index 990a2ca..0f3ab6c 100644
> --- a/xen/arch/x86/hvm/irq.c
> +++ b/xen/arch/x86/hvm/irq.c
> @@ -330,6 +330,10 @@ void hvm_set_callback_via(struct domain *d, uint64_t via)
>           (via_type > HVMIRQ_callback_vector) )
>          via_type = HVMIRQ_callback_none;
>  
> +    if ( via_type != HVMIRQ_callback_vector &&
> +         (!has_vlapic(d) || !has_vioapic(d) || !has_vpic(d)) )
> +        return;

I think the logic needs to be slightly more complicated.

Without a vlapic, all callback types are invalid.

Without an ioapic/pic, _gsi and _pci_intx are invalid, but _vector is
possible.

Other issues with this area of code (not caused by you) are the fact
there is no error flagged from this setup, and that via_type is not
exposed in the Xen ABI.  Both of these should be looked into by someone
with some copious free time, but are not impediments to this patch series.

~Andrew

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